Curcumin I, curcumin II (monodemethoxycurcumin) and curcumin III (bisdemethoxycurcumin) from Curcuma longa were assayed for their cytotoxicity, antioxidant and anti-inflammatory activities. These compounds showed activity against leukemia, colon, CNS, melanoma, renal, and breast cancer cell lines. The inhibition of liposome peroxidation by curcumins I-III at 100 microg/ml were 58, 40 and 22%, respectively. The inhibition of COX-I and COX-II enzymes by the curcumins was observed. Curcumins I-III were active against COX-I enzyme at 125 microg/ml and showed 32, 38.5 and 39.2% inhibition of the enzyme, respectively. Curcumins I-III also showed good inhibition of the COX-II enzyme at 125 mg/ml with 89.7, 82.5 and 58.9% inhibition of the enzyme, respectively.