The Medication Adherence and BP Control Trial (ABC Trial) is a randomized, controlled, multi-site, medication adherence and blood pressure (BP) control trial in an economically disadvantaged and multi-cultural population of hypertensive patients followed in primary care practices. To date, no other such trial has been published in which objective measures of adherence (electronic pill bottles) were used to assess the effectiveness of these behavioral interventions for hypertension. This study tested a combination of commercially-available interventions that can be easily accessed by health care providers and patients, and therefore may provide a real-world solution to the problem of non-adherence among hypertensives. The aim of the ABC Trial was to test the effectiveness of a stepped care intervention in improving both medication adherence to an antihypertensive medication regimen and BP control. Step 1 of the intervention employed home Self-BP Monitoring (SBPM); at this stage, there were two arms: (1) Usual Care (UC) and (2) Intervention. At Step 2, patients in the intervention arm whose BP had not come under control after 3 months were further randomized to one of two conditions: (1) continuation of SBPM (alone) or (2) continuation of SBPM plus telephone-based nurse case management (SBPM+NCM). Electronic Medication Event Monitoring (MEMS) was the primary measure of medication adherence, and in-office BP was the primary measure of hypertension control. We present an overview of the study design, details of the administrative structure of the study and a description of clinical site recruitment, patient recruitment, and follow-up assessments.