During the Spring 2000 academic semester at the University of Georgia, an experiment involving mode effects between four modes of administration of the Core Institute (Core Institute, Southern Illinois University, Carbondale) survey of drug and alcohol use was conducted by the Survey Research Center among currently enrolled students. The purpose of the study was to examine differences in administering the Core survey by telephone, mail, web-based, and IVR (Interactive Voice Recognition) techniques. The study had three specific aims. First, to examine the degree to which each method produced a sample of students representative of the total population of University of Georgia students, second, to examine relative response rates for each method, and third, to examine substantive differences in frequency and prevalence of alcohol and drug use.