Chloroquine is a drug with over 60 years of sale clinical use in the treatment of malaria. The multiple mechanisms of chloroquine action have appeared to be useful in the therapy of many miscellaneous disorders well beyond its original antimalarial purposes. This paper is focused on the application of chloroquine for the treatment of malaria, porphyria cutanea tarda, rheumatoid arthritis, palindromic rheumatism and lupus. The possibility of the use of chloroquine in the therapy of other disorders such as diabetes mellitus, AIDS, hyperlipidemia, sarcoidosis, hypercalcemia, and melanoma is reviewed. Mechanisms of action of the drug as well as side effects on metabolism are discussed in view of recent discoveries.