This article is designed as one of a series which will discuss certain aspects of validity in surveys. The first article, which appears below, examines two current concepts of validity (as predictive accuracy, and as a matter of interpretation), reviews the literature on the subject, and presents some of the results of a specially designed survey in Denver which showed that the validity of even simple “factual” responses may often be open to question. Subsequent articles will discuss the effect of the interviewer on the validity of survey results and the variations in validity according to respondent characteristics and other variables. Hugh j. Parry was formerly Acting Director of the Opinion Research Center of the University of Denver, and is at present Director of Publications for the Anti-Defamation League. Helen M. Crossley, formerly Senior Analyst at the Opinion Research Center, is now with the Attitude Research Branch of the Armed Forces Information and Education Division.