No data exist on any association between combined cyclosporine A (Cy A) and dihydropyridine (DHP) medication and the effect of periodontal treatment on the occurrence of gingival overgrowth (GO) among renal transplant recipients. Clinical data on 27 renal transplant recipients treated with Cy A are presented here, including determinations of serum creatinine, whole blood Cy A concentration, existence of DHP treatment, and periodontal status. GO was classified into four categories according to the clinical changes: score 0 = no GO; score 1 = mild GO; score 2 = moderate GO; and score 3 = severe GO. All participants received hygiene phase periodontal treatment and gingivectomies were performed on 10 who originally had score 2 or 3 GO and pocketing. Fourteen (14) of the recipients had no overgrown gingiva or less than at the initial examination, and none of them had GO score 2 or 3 at the time of re-examination (group A). Thirteen (13) participants had more overgrown gingiva than initially or developed score 2 GO after gingivectomies (group B). Group B included significantly more DHP-medicated recipients than group A (6/13 and 1/14 respectively; P < 0.03). The concomitant administration of Cy A and DHP resulted in a significantly increased percentage of score 2 overgrown gingival units as compared with Cy A alone (P < 0.03). It is concluded that combined treatment with Cy A and DHP is a significant risk factor for progression or recurrence of GO after periodontal treatment among susceptible patients.