This article reviews the epidemiological data on drug-induced acute akathisia, examining studies in which akathisia was the primary focus as well as those in which it was one of a number of drug side effects studied. The studies are diverse in methodology and suffer from many limitations. Incidence rates for acute akathisia with conventional neuroleptics vary from 8 to 76 percent, with 20 to 30 percent being a conservative estimate; preliminary evidence suggests that the newer atypical antipsychotic drugs are less likely to produce acute akathisia. A number of nonneuroleptic drugs--in particular the serotonin-specific reuptake inhibitors--have been implicated in the development of akathisia, but the epidemiological data are limited. Risk factors for neuroleptic-induced akathisia are not completely understood. Drug dose, rate of increment of dose, and drug potency seem to be important, but the role of sociodemographic factors and other treatment-related variables is modest. Drug-induced parkinsonism is significantly correlated with akathisia. Evidence for iron deficiency as a risk factor is conflicting, and its contribution is likely to be minor.