Abstract: Despite wide variation in prevalence rates for all sexual dysfunctions depending on the population and methodology in question, the numbers are staggering. With general prevalence figures for sexual problems reported to be as high as 40% in women and 28% in men, sexual difficulties seem close to normative. Once relegated strictly to sex therapists and sexologists, the assessment of sexual function is increasingly considered an integral part of an overall health assessment. This chapter focuses on the assessment of female and male sexual dysfunctions in adults. It begins with a review of the nature of the conditions, which is followed by a review of clinical assessment instruments designed for the assessment purposes of (a) diagnosis, (b) case conceptualization and treatment planning, and (c) treatment monitoring and evaluation. Recommendations are included for instruments with the greatest scientific support and for assessing these conditions in a clinically sensitive manner.