Summary:The present communication reviews reasons to perform rescreening of chlamydia-infected persons. It brings up dif® culties to differentiate between relapse and reinfection. Studies on follow-up of chlamydia-positive cases after therapy are reviewed. It also highlights reasons for therapeutic failure, like compliance, pharmacological factors, including poor bioavailability, wrong dose regimens, lack of adherence to drug intake, neglect of partner noti® cation and concomitant therapy in consorts, possible development of resistance to drugs generally prescribed, false negative or false positive diagnostic tests and reinfection from extra-genital not`cured' sites. The review points to the need to establish programmes for routine rescreening of chlamydia-infected persons.