The spectrum of neurological complications associated with heroin addiction has changed in the past six years because of the progressive knowledge of the neurological complications related to HIV infection. We reviewed 48 heroin addicts with neurological complications and 452 heroin overdose who were seen in the Emergency Unit of our hospital during 1988 and the publications since 1967. Regarding the overdose we present the results of a prospective study leading to determine the causes. We emphasize the relationship with the level of total morphine in serum, instead of conjugate morphine, and with the presence of high levels of benzodiazepines found in the plasma rather than an hypothetic hypersensitivity phenomenon. We resume the neurological complications related with heroin addiction: spongiform leukoencephalopathy, epileptic seizures, stroke, transverse myelopathy and neuromuscular complications such mononeuropathy, plexopathy, acute inflammatory demyelinating polyradiculoneuropathy, rhabdomyolysis, fibrosing myopathy, musculoskeletal syndrome and acute bacterial myopathy. Some of such complications (i.e. transverse myelitis, polyradiculoneuropathy, leucoencephalopathy) must rise the suspicion of an HIV infection. Likewise, in patients assisted for overdosage we believe it's necessary rule out myoglobinuria by means of CPK serum levels and detection of urine hematic pigments without red blood cels in the urine sediment, in order to prevent and treat the renal failure. We report the results of muscular biopsy found in the musculoskeletal syndrome, which are similar to those found in alcoholic myopathy. Finally, we describe the clinical and diagnostic aspects in an unusually neuromuscular complication: the acute bacterial myopathy.