This study investigated the prevalence of gingival hyperplasia in subjects who were undergoing treatment with a calcium channel blocker, nifedipine, in dentate and edentulous subjects. In addition, the relationship between gingival hyperplasia and 5 other variables (duration of nifedipine intake, dose, age, oral hygiene index, and number of teeth) was investigated. Results of statistical analyses showed overwhelming evidence that the percent of nifedipine subjects with gingival hyperplasia was greater than that of the control subjects (P < 0.05) and that, across treatment group, the percent of dentate subjects with hyperplasia was significantly higher than that for edentulous subjects (P < 0.05). The chi2 test showed a strong univariate relationship between gingival hyperplasia and, separately, oral hygiene and number of teeth. For 24% of the subjects with gingival hyperplasia index (GHI) values of 2 or 3, gingivectomy was performed, and the tissues were prepared for histological examination. Microscopic examination of the biopsy material showed findings similar to those from previously reported cases of nifedipine- or phenytoin-induced hyperplasia.