PURPOSE: Determine the risk of cancer in statin users. METHODS: Risk of cancer in up to 9.4 years after first recorded receipt of statins was evaluated in subscribers of an integrated health care program in northern California. Statin use and cancer development were ascertained from the program’s pharmacy records and cancer registry from August 1994 to December 2003. RESULTS: Most of the 361,859 statin users received lovastatin, simvastatin or both. Results are presented from analyses with 2-year lag and use for over 5 years. Most of the observed associations were likely due to chance or confounding. The few associations that seemed less readily explainable were increased risk of cancers of the thyroid, esophagus and urinary tract and decreased risk of colon cancer in men. Increased risk of lung cancer was the only nominally statistically significant positive association in women and could be partially attributable to their smoking habits. CONCLUSIONS: Overall this study provided no strong evidence of either causation or prevention of cancer by statins.