Chlamydial eye infection was detected in 28 of 983 ophthalmological patients with conjunctivitis or keratoconjunctivitis, with a peak frequency of over 9% in patients aged 16-20 years and with decreasing frequency thereafter. In patients aged 1 to 15 years chlamydial conjunctivitis was not observed. Chlamydial eye infection could not be detected in patients at a venereal diseases clinic, though chlamydial genital infection was rather frequent in these patients. Nor was Chlamydia trachomatis found in the eyes of healthy young adults. In patients with proved chlamydial conjunctivitis unilateral symptoms were the rule. Pseudoptosis was the most conspicuous presentation in two cases. A prolonged course can be expected in chlamydial eye infection if the condition is unrecognised and effective treatment delayed. The venereal background of the condition must also influence the management.