The goal of these studies was to determine if chronic (+)methamphetamine ((+)METH) administration affects the production of anti-(+)METH antibodies during active immunization of rats. Active immunization for the treatment of chronic drug abuse has been proposed for drugs such as cocaine and nicotine. However, studies have not adequately addressed whether continual drug use during treatment would affect the development of an immune response. For the current studies, male Sprague-Dawley rats were immunized with either keyhole limpet hemocyanin (KLH; control group) or a (+)METH hapten ((+)METH with a six carbon spacer group at the para position of the ring structure)-KLH conjugate. The (+)METH-KLH animals were further divided into two groups. One group was immunized with no subsequent administration of (+)METH, while the other group was immunized and repeatedly challenged (twice a week throughout the study) with an i.p. dose of 3 mg/kg (+)METH. The results showed that the two groups of (+)METH-KLH immunized rats developed and maintained anti-(+)METH antibody titers. The anti-(+)METH immune responses of the two groups were not statistically different (P < 0.05) as measured by serum titers and the relative antibody affinities. These data suggest that repeated administration of (+)METH does not affect the generation of an anti-(+)METH antibody response in actively immunized rats.