Low sperm count often has no obvious physical signs, and this chapter explains what men may and may not notice. Difficulty conceiving is the main symptom, though depending on the underlying cause there may be other signs, such as problems with sexual function, changes or pain around the testicles, or reduced body hair. The chapter then explains how oligospermia is diagnosed through semen analysis at a fertility clinic, including the advice to avoid ejaculation for a few days before giving a sample, and what the analysis can reveal about sperm health.