@@ -428,6 +428,15 @@ def sum(self, axis=None, dtype=None, out=None):
             copy=False
         )
 
+    @with_doc(np.nansum)
+    def nansum(self, axis=None, dtype=None, out=None):
+        import numpy as np
+        return Quantity(
+            np.nansum(self.magnitude, axis, dtype, out),
+            self.dimensionality,
+            copy=False
+        )
+        
     @with_doc(np.ndarray.fill)
     def fill(self, value):
         self.magnitude.fill(value)
 
@@ -17,6 +17,12 @@ def test_sum(self):
         self.assertQuantityEqual(self.q.sum(0), [4, 6]*pq.m)
         self.assertQuantityEqual(self.q.sum(1), [3, 7]*pq.m)
 
+    def test_nansum(self):
+        import numpy as np
+        qnan = [[1,2], [3,4], [np.nan,np.nan]] * pq.m
+        self.assertQuantityEqual(qnan.nansum(), 10*pq.m )
+        self.assertQuantityEqual(qnan.nansum(0), [4,6]*pq.m )
+
     def test_fill(self):
         self.q.fill(6 * pq.ft)
         self.assertQuantityEqual(self.q, [[6, 6], [6, 6]] * pq.ft)
 
@@ -3,6 +3,7 @@
 from .. import units as pq
 from ..uncertainquantity import UncertainQuantity
 from .common import TestCase
+import numpy as np
 
 
 class TestUncertainty(TestCase):
@@ -62,20 +63,17 @@ def test_uncertainquantity_divide(self):
         self.assertQuantityEqual((1/a).uncertainty, [0.1, 0.05]/pq.m)
 
     def test_uncertaintity_mean(self):
-        import numpy as np
         a = UncertainQuantity([1,2], 'm', [.1,.2])
         mean0 = np.sum(a)/np.size(a) # calculated traditionally
         mean1 = a.mean()        # calculated using this code
         self.assertQuantityEqual(mean0, mean1)
 
     def test_uncertaintity_nanmean(self):
-        import numpy as np
         a = UncertainQuantity([1,2], 'm', [.1,.2])
         b = UncertainQuantity([1,2,np.nan], 'm', [.1,.2,np.nan])
         self.assertQuantityEqual(a.mean(),b.nanmean())
 
     def test_uncertainquantity_subtract(self):
-        import numpy as np
         a = UncertainQuantity(1, 'm', 1)
         b = a.copy() # different object
         self.assertQuantityEqual(a-a, UncertainQuantity(0, 'm', 0))
@@ -84,3 +82,9 @@ def test_uncertainquantity_subtract(self):
     def test_uncertainty_sqrt(self):
         a = UncertainQuantity([1,2], 'm', [.1,.2])
         self.assertQuantityEqual(a**0.5, a.sqrt())
+
+    def test_uncertainty_nansum(self):
+        uq = UncertainQuantity([1,2], 'm', [1,1])
+        uq_nan = UncertainQuantity([1,2,np.nan], 'm', [1,1,np.nan])
+        self.assertQuantityEqual(np.sum(uq), np.nansum(uq))
+        self.assertQuantityEqual(np.sum(uq), np.nansum(uq_nan))
@@ -210,6 +210,16 @@ def sum(self, axis=None, dtype=None, out=None):
             copy=False
         )
 
+    @with_doc(np.nansum)
+    def nansum(self, axis=None, dtype=None, out=None):
+        import numpy as np
+        return UncertainQuantity(
+            np.nansum(self.magnitude, axis, dtype, out),
+            self.dimensionality,
+            (np.nansum(self.uncertainty.magnitude**2, axis))**0.5,
+            copy=False
+        )
+
     @with_doc(np.ndarray.mean)
     def mean(self, axis=None, dtype=None, out=None):
         return UncertainQuantity(