The objective of this randomized controlled trial was to assess the effects of a 1-year behavioral contract intervention on immunosuppressant therapy (IST) adherence and healthcare utilizations and costs among adult renal transplant recipients (RTRs). The sample included adult RTRs who were at least 1 year posttransplant, taking tacrolimus or cyclosporine and served by a specialty pharmacy. Pharmacy refill records were used to measure adherence and monthly questionnaires were used to measure healthcare utilizations. Direct medical costs were estimated using the 2009 Medicare Expenditure Panel Survey. Adherence was analyzed using the GLM procedure and the MIXED procedure of SAS. Rate ratios and 95% confidence intervals were estimated to quantify the rate of utilizing healthcare services relative to treatment assignment. One hundred fifty RTRs were enrolled in the study. Intervention group RTRs (n = 76) had higher adherence than control group RTRs (n = 74) over the study period (p < 0.01). And 76.1% of the intervention group compared with 42.7% of the control group was not hospitalized during the 1-year study period (RR = 1.785; 95% CI: 1.314, 2.425), resulting in cost savings. Thus, evidence supports using behavioral contracts as an effective adherence intervention that may improve healthcare outcomes and lower costs. © Copyright 2013 The American Society of Transplantation and the American Society of Transplant Surgeons.