During ten years of study of Chlamydia trachomatis eye infections, trachoma was diagnosed in 14 Danish patients with onset during childhood. Clinical findings in the eye were characteristic of classical trachoma. The infecting C trachomatis immunotype was identified in all but one case. At the time of diagnosis, seven patients were still children (6 to 10 years of age), three were teenagers, and four were adults. In five young girls the disease was extremely severe. Delay in proper diagnosis and adequate therapy contributed to the prolongation and severity of the disease. Failure to diagnose is attributed to widespread opinion and teaching of physicians in Western countries that trachoma eye disease has disappeared. Studies of family members and other contacts of the patients contributed to an understanding of the pathogenesis of this disease. The source of initial eye infection with C trachomatis organisms in these cases was thought to be the birth canal. It was further postulated that reinfection of the eyes of these children occurred either from a reservoir in their own or their mother's genital tract.