Genital chlamydia infections are the most frequently diagnosed bacterial sexually transmitted infection (STI) worldwide. Infections with chlamydia trachomatis are not notifiable in Germany. Since 2002, a STI sentinel surveillance including 243 sentinel sites has been set up in Germany. Between January 2003 and June 2006, 6.7% of 46,168 chlamydia tests were positive. Of the 1547 positive patients, 64.3% were women and the median age was 26 years. In this group, 60.4% of women and 29.3% of men were of non-German origin. Heterosexual contacts were stated as the possible source of infection for 42.9% of men and 26.4% of women. A total of 16.1% men and 38.6% women reportedly "always" used condoms with others than their permanent partner. The awareness of chlamydia infections needs to be improved among physicians, patients and the general population.