The present study was conducted to determine the clinical effects of nifedipine on the gingiva of 97 patients. Patients were examined for changes in periodontal status and divided into subgroups, based on their age, gender, duration of drug intake, presence/absence of plaque and gingival inflammation, and according to the presence and severity of gingival overgrowth. Gingival overgrowth was noticed in 29% of the patients. Among the recorded parameters, duration of drug intake, presence/severity of gingival inflammation, and gender seemed to have the greatest effect on the development of gingival overgrowth. Patients with higher gingival inflammation scores, those on nifedipine medication for more than 4 years, and males were likely to have an increased tendency for higher incidence and severity of gingival overgrowth. The findings of the present study suggest that nifedipine medication induces gingival overgrowth and that certain local factors are involved in the pathogenesis of drug-induced gingival overgrowth. However, individual ability and sensitivity to metabolize the drug and its metabolites also seem to be important etiological factors.