diff --git a/SimPEG/ObjFunction.py b/SimPEG/ObjFunction.py
index 7d08b9fc..47354b4b 100644
--- a/SimPEG/ObjFunction.py
+++ b/SimPEG/ObjFunction.py
@@ -164,7 +164,7 @@ class BaseObjFunction(object):
 
         R = self.data.residualWeighted(m, u=u)
 
-        dmisfit = self.data.prob.Jt(m, self.data.Wd * R, u=u)
+        dmisfit = self.data.prob.Jtvec(m, self.data.Wd * R, u=u)
 
         return dmisfit
 
@@ -209,7 +209,7 @@ class BaseObjFunction(object):
         R = self.data.residualWeighted(m, u=u)
 
         # TODO: abstract to different norms a little cleaner.
-        #                                                 \/ it goes here. in l2 it is the identity.
-        dmisfit = self.data.prob.Jt_approx(m, self.data.Wd * self.data.Wd * self.data.prob.J_approx(m, v, u=u), u=u)
+        #                                                     \/ it goes here. in l2 it is the identity.
+        dmisfit = self.data.prob.Jtvec_approx(m, self.data.Wd * self.data.Wd * self.data.prob.Jvec_approx(m, v, u=u), u=u)
 
         return dmisfit
diff --git a/SimPEG/Problem.py b/SimPEG/Problem.py
index 314af81f..c6f381f5 100644
--- a/SimPEG/Problem.py
+++ b/SimPEG/Problem.py
@@ -70,7 +70,7 @@ class BaseProblem(object):
     def ispaired(self): return self.data is not None
 
     @Utils.timeIt
-    def J(self, m, v, u=None):
+    def Jvec(self, m, v, u=None):
         """
             :param numpy.array m: model
             :param numpy.array v: vector to multiply
@@ -100,7 +100,7 @@ class BaseProblem(object):
         raise NotImplementedError('J is not yet implemented.')
 
     @Utils.timeIt
-    def Jt(self, m, v, u=None):
+    def Jtvec(self, m, v, u=None):
         """
             :param numpy.array m: model
             :param numpy.array v: vector to multiply
@@ -114,7 +114,7 @@ class BaseProblem(object):
 
 
     @Utils.timeIt
-    def J_approx(self, m, v, u=None):
+    def Jvec_approx(self, m, v, u=None):
         """
 
             :param numpy.array m: model
@@ -126,10 +126,10 @@ class BaseProblem(object):
             Approximate effect of J on a vector v
 
         """
-        return self.J(m, v, u)
+        return self.Jvec(m, v, u)
 
     @Utils.timeIt
-    def Jt_approx(self, m, v, u=None):
+    def Jtvec_approx(self, m, v, u=None):
         """
             :param numpy.array m: model
             :param numpy.array v: vector to multiply
@@ -140,7 +140,7 @@ class BaseProblem(object):
             Approximate transpose of J*v
 
         """
-        return self.Jt(m, v, u)
+        return self.Jtvec(m, v, u)
 
     def fields(self, m):
         """