Although numerous studies have been conducted on abused drugs, most focus on the problems of addiction (dependence) and their neurotoxicities. Now accumulated data have demonstrated that the genotoxicity and/or carcinogenicity of abused drugs can also be detrimental to our health. In this review, commonly abused substances, including LSD, opiates (diacetylmorphine, morphine, opium and codeine), cocaine, cannabis, betel quid and khat, are discussed for their potential genotoxicity/carcinogenicity. The available literature in the held, although not as abundant as for neurotoxicity, clearly indicates the capability of abused drugs to induce genotoxicity.