The Office of Behavioral and Social Sciences Research (OBSSR) is pleased to offer a series of symposia to provide NIH staff with expertise relevant to randomized clinical trials (RCTs) with behavioral interventions. The series assumes the audience has basic or general understanding of RCT design and implementation. The emphasis is on issues of particular concern to RCTs in which the intervention (i.e., "treatment") is behavioral, whether alone or in combination with biomedical treatments. (The outcomes may be behavioral or biomedical.) These issues may or may not be unique to behavioral RCTs (i.e., quantitative vs. qualitative differences in the nature of behavioral vs. biomedical RCTs).