A substantial number of patients who meet criteria for a prodromal syndrome for first psychosis are treated with antipsychotic and/or antidepressant medications. There is suggestive evidence that both classes of medication may reduce prodromal symptoms. This longitudinal study examined the relation of antipsychotic and antidepressant medication with prodromal symptom severity at baseline and 6-month follow-up. Participants met Structured Interview for Prodromal Syndromes (SIPS) criteria for the prodrome, and were evaluated at eight centers as part of the North American Prodrome Longitudinal Study (NAPLS). Symptom ratings (positive, negative, disorganized and general) and data on antipsychotics, SSRIs, and other antidepressant medications were obtained at baseline and 6-month follow-up. Analyses revealed that all symptom dimensions declined in severity over time, but there were differences in the magnitude of the decline as a function of antipsychotic medication. Those never on antipsychotics showed less reduction in positive and disorganized symptoms over time. SSRIs and other antidepressants were not linked with declines in symptom severity. Consistent with findings from small-sample, clinical trials, the present results suggest that atypical antipsychotics may be effective in reducing the severity of attenuated positive symptoms associated with the prodrome to psychotic disorders. Limitations of the present study are noted, including the fact that it is not a randomized trial, and data on duration and dosage of medication and 2-year follow-up were not available for most participants. The results are discussed in light of the relative risks and benefits of preventive interventions, both medication and cognitive therapies, and the importance of future clinical trials.