diff --git a/constraint.cpp b/constraint.cpp
index 22252fa..66b97e6 100644
--- a/constraint.cpp
+++ b/constraint.cpp
@@ -31,6 +31,7 @@ char *Constraint::DescriptionString(void) {
         case SAME_ORIENTATION:  s = "same-orientation"; break;
         case ANGLE:             s = "angle"; break;
         case PARALLEL:          s = "parallel"; break;
+        case PERPENDICULAR:     s = "perpendicular"; break;
         case EQUAL_RADIUS:      s = "eq-radius"; break;
         case COMMENT:           s = "comment"; break;
         default:                s = "???"; break;
@@ -425,6 +426,18 @@ void Constraint::MenuConstrain(int id) {
             AddConstraint(&c);
             break;
 
+        case GraphicsWindow::MNU_PERPENDICULAR:
+            if(gs.vectors == 2 && gs.n == 2) {
+                c.type = PERPENDICULAR;
+                c.entityA = gs.vector[0];
+                c.entityB = gs.vector[1];
+            } else {
+                Error("Bad selection for perpendicular constraint.");
+                return;
+            }
+            AddConstraint(&c);
+            break;
+
         case GraphicsWindow::MNU_COMMENT:
             c.type = COMMENT;
             c.comment.strcpy("NEW COMMENT -- DOUBLE-CLICK TO EDIT");
@@ -942,6 +955,7 @@ void Constraint::GenerateReal(IdList<Equation,hEquation> *l) {
             break;
         }
 
+        case PERPENDICULAR:
         case ANGLE: {
             Entity *a = SS.GetEntity(entityA);
             Entity *b = SS.GetEntity(entityB);
@@ -965,8 +979,16 @@ void Constraint::GenerateReal(IdList<Equation,hEquation> *l) {
                 Expr *dot = (ua->Times(ub))->Plus(va->Times(vb));
                 c = dot->Div(maga->Times(magb));
             }
-            Expr *rads = exA->Times(Expr::From(PI/180));
-            AddEq(l, c->Minus(rads->Cos()), 0);
+            if(type == ANGLE) {
+                // The direction cosine is equal to the cosine of the
+                // specified angle
+                Expr *rads = exA->Times(Expr::From(PI/180));
+                AddEq(l, c->Minus(rads->Cos()), 0);
+            } else {
+                // The dot product (and therefore the direction cosine)
+                // is equal to zero, perpendicular.
+                AddEq(l, c, 0);
+            }
             break;
         }
 
diff --git a/drawconstraint.cpp b/drawconstraint.cpp
index 3d40e19..1803f5c 100644
--- a/drawconstraint.cpp
+++ b/drawconstraint.cpp
@@ -373,6 +373,43 @@ void Constraint::DrawOrGetDistance(Vector *labelPos) {
             break;
         }
 
+        case PERPENDICULAR: {
+            Vector u, v;
+            Vector rn, ru;
+            if(workplane.v == Entity::FREE_IN_3D.v) {
+                rn = gn;
+                ru = gu;
+            } else {
+                Entity *normal = SS.GetEntity(workplane)->Normal();
+                rn = normal->NormalN();
+                ru = normal->NormalV(); // ru meaning r_up, not u/v
+            }
+
+            for(int i = 0; i < 2; i++) {
+                Entity *e = SS.GetEntity(i == 0 ? entityA : entityB);
+
+                if(i == 0) {
+                    // Calculate orientation of perpendicular sign only
+                    // once, so that it's the same both times it's drawn
+                    u = e->VectorGetNum();
+                    u = u.WithMagnitude(16/SS.GW.scale);
+                    v = (rn.Cross(u)).WithMagnitude(16/SS.GW.scale);
+                    if(fabs(u.Dot(ru)) < fabs(v.Dot(ru))) {
+                        SWAP(Vector, u, v);
+                    }
+                    if(u.Dot(ru) < 0) u = u.ScaledBy(-1);
+                }
+
+                Vector p = e->VectorGetRefPoint();
+                Vector s = p.Plus(u).Plus(v);
+                LineDrawOrGetDistance(s, s.Plus(v));
+
+                Vector m = s.Plus(v.ScaledBy(0.5));
+                LineDrawOrGetDistance(m, m.Plus(u));
+            }
+            break;
+        }
+
         case PARALLEL: {
             for(int i = 0; i < 2; i++) {
                 Entity *e = SS.GetEntity(i == 0 ? entityA : entityB);
diff --git a/graphicswin.cpp b/graphicswin.cpp
index 289acde..08bb54d 100644
--- a/graphicswin.cpp
+++ b/graphicswin.cpp
@@ -86,6 +86,7 @@ const GraphicsWindow::MenuEntry GraphicsWindow::menu[] = {
 { 1, "At &Midpoint\tShift+M",               MNU_AT_MIDPOINT,    'M'|S,  mCon  },
 { 1, "S&ymmetric\tShift+Y",                 MNU_SYMMETRIC,      'Y'|S,  mCon  },
 { 1, "Para&llel\tShift+L",                  MNU_PARALLEL,       'L'|S,  mCon  },
+{ 1, "&Perpendicular\tShift+P",             MNU_PERPENDICULAR,  'P'|S,  mCon  },
 { 1, "Same Orient&ation\tShift+A",          MNU_ORIENTED_SAME,  'A'|S,  mCon  },
 { 1, NULL,                                  0,                          NULL  },
 { 1, "Comment\tShift+C",                    MNU_COMMENT,        'C'|S,  mCon  },
diff --git a/sketch.h b/sketch.h
index 22f453d..d550b8a 100644
--- a/sketch.h
+++ b/sketch.h
@@ -456,6 +456,7 @@ public:
     static const int SAME_ORIENTATION   = 110;
     static const int ANGLE              = 120;
     static const int PARALLEL           = 121;
+    static const int PERPENDICULAR      = 122;
     static const int EQUAL_RADIUS       = 130;
 
     static const int COMMENT            = 1000;
diff --git a/ui.h b/ui.h
index 68588f8..0ee602e 100644
--- a/ui.h
+++ b/ui.h
@@ -196,6 +196,7 @@ public:
         MNU_HORIZONTAL,
         MNU_VERTICAL,
         MNU_PARALLEL,
+        MNU_PERPENDICULAR,
         MNU_ORIENTED_SAME,
         MNU_COMMENT,
     } MenuId;
diff --git a/wishlist.txt b/wishlist.txt
index 1bcac2b..21508c2 100644
--- a/wishlist.txt
+++ b/wishlist.txt
@@ -8,7 +8,6 @@ auto-generate circles and faces when lathing
 copy the section geometry to other end when sweeping
 cylindrical faces
 draw explicit edges
-perpendicular constraint
 
 
 long term