OBJECTIVES: Non-adherence to medication regimens after organ transplantation is a major risk factor for acute rejection and graft loss, however, there is limited data quantifying the associated risk. This study examines the association between adherence to immunosuppressant therapy and rejection in liver and kidney organ transplant recipients. METHODS: This is a randomized, cross sectional analysis.  Adherence to immunosuppressants was assessed by administering the Immunosuppresive Therapy Adherence Scale (ITAS) to patients at the time of their clinic appointment.  Rejection was defined as biopsy proven rejection. The number of biopsies, number of rejections, rejection severity and length of hospital stay due to rejection were collected.  Immunosuppressant regimens, levels, number of dose changes, and number of tablets/capsules per day were obtained. Logistic regression model was used to determine the association between rejection and adherence, gender and number of tablets/capsules consumed per day. RESULTS: A total of 67 patients were included in this study, from which 21(31%) were males with an average age of 51 years, SD=11.6.  There were 49 (73.1%) kidney recipients, 14 (20.9%) liver recipients and 4 (5.9%) combination.  At least one rejection was observed in 26 (38.8%) of the patients, from which 18 (69.2%), 6 (23.1%) and 2 (7.7%) were kidney, liver and combination, respectively.  A total of 35 (52.3%) of the patients were found to be non-adherent with their medications, from which 18 (51.4%) had at least one rejection.  Patients were taking an average of 18 tablets/capsules per day.  The logistic regression showed that gender and tablets/capsules consumed per day had no impact on rejection, however, non-adherence is significantly associated with rejection (OR=0.264, 95% CI is 0.089-0.784).  Non adherent patient are 74% more likely to have a rejection compared to adherent patients. CONCLUSIONS: Non-adherence to immunosuppressive medication results in increased rejection rates in kidney and liver transplant recipients.