The present review is motivated by the fact that 100 years have passed since the first cancer case in a chromium worker was reported in Scotland. Old and recent case reports and epidemiological studies among chromate workers are reviewed to elucidate the importance of valency states and water solubility of chromium compounds for carcinogenic potency. It is concluded that all chromium[VI] compounds should be considered carcinogenic among exposed populations, and that no evidence has been presented indicating that human exposure to chromium[III] is associated with increased cancer risk. Strong evidence has been presented that zinc chromate is a potent carcinogen and suggests that calcium chromate may be a potent carcinogen. Evidence also suggests that water-soluble chromates in general may be more potent carcinogens than those with low solubility. Primary and secondary prevention of chromate-related cancer and the success in preventive measures are briefly discussed, and recommendations for future research are made.