Gingival enlargement comprises any clinical condition in which an increase in the size of the gingiva is observed. It is a side effect associated with some distinct classes of drugs, such as anticonvulsants, immunosuppressant, and calcium channel blockers. Among calcium channel blockers, nifedipine causes gingival enlargement in about 10% of patients, whereas the incidence of amlodipine, a third-generation calcium channel blocker, induced gingival enlargement is very limited. Because the calcium antagonists, albeit to a variable degree, act as inhibitors of P-glycoprotein (P-gp), the gene product of multidrug resistance 1 (MDR1), and inflammation may modify P-gp expression. We hereby, report a case of amlodipine-induced gingival enlargement with MDR1 3435C/T polymorphism, associated with inflammatory changes due to plaque accumulation, in a 50-year-old hypertensive male patient. The genotype obtained for the polymorphism was a heteromutant genotype, thus supporting the contention that the MDR1 polymorphism may alter the inflammatory response to the drug.