In this paper, the author aims to provide novice researchers with an understanding of the general problem of validity in social science research and to acquaint them with approaches to developing strong support for the validity of their research. She provides insight into these two important concepts, namely (1) validity; and (2) reliability, and introduces the major methods to assess validity and reliability as they relate to behavioural research. The paper is organised as follows. The first section presents what reliability of measurement means and the techniques most frequently used to estimate reliability. Three important questions researchers frequently ask about reliability are discussed: (1) what affects the reliability of a test?; (2) how can a test be made more reliable?; and (3) what is a satisfactory level of reliability? The second section presents what validity means and the methods to develop strong support for validity in behavioural research. Four types of validity are introduced: (1) statistical conclusion validity; (2) internal validity; (3) construct validity; and (4) external validity. Approaches to substantiate them are also discussed. The paper concludes with a summary and suggestions. (Contains 2 figures.)