The aim of this review is to evaluate the side effects of some drug therapies on the gingival tissue in certain susceptible individuals. Phenytoin, cyclosporine-A and a variety of calcium channel blockers have been shown to produce gingival overgrowth. In this paper the pharmacodynamics and pharmacokinetics of these drugs, the pathogenesis, the clinical aspect of the enlargement and its treatment are examined. Several of the reviewed theories on pathogenesis are well documented in the literature, while others are controversial and less described. The old term gingival hyperplasia is not exact because histologically an increase in the number of fibroblasts has not been demonstrated, but an increase has been found out in the amount of collagen fibers and noncollagenous proteins in the connective tissue. The clinical findings have the same characteristics both in location and growth pattern while prevention is primarily directed at the removal of local irritant factors. The prevalence and severity of gingival enlargement increase in heart transplant patients who are often medicated with cyclosporin and channel blockers.