We have investigated the antiproliferative effect of curcumin, an antitumor agent with antioxidant and anti-inflammatory properties, against a variety of transformed and nontransformed cell types. At equimolar concentrations ranging from 6.25 to 50 microM, curcumin inhibited DNA synthesis, as revealed by 3H-incorporation, in five leukemia lines, three nontransformed hematopoietic progenitor cell populations, and four nontransformed fibroblastic cell lines in a concentration-dependent manner. Curcumin also inhibited the cellular growth of both transformed and nontransformed cells in clonogenic assays. Without discriminating between transformed or nontransformed cells, the inhibition of cell proliferation by curcumin was not always associated with programmed cell death. These findings have implications for developing curcumin-based anticancer and anti-inflammation therapies.