Water is a substrate for many biochemical reactions. If D2O is ingested, it will be incorporated into proliferating cells. We hypothesized that rapidly proliferating cancer cells would become preferentially labeled with 2H which would allow visualization by deuterium MRI following a short in vivo D2O labeling period. We initiated systemic D2O labeling in HT-29 and MiaPaCa-2 xenograft models and performed deuterium MRI following 7 and 14 days of in vivo tumor growth and labeling. We show that small tumors could be distinguished from normal tissue by the incorporation D2O into lipids with a greater sensitivity and selectivity than anatomical MRI.