The relationship between the infecting Chlamydia trachomatis serovar and the clinical manifestations of genital tract infection was evaluated in a study of 155 women attending a sexually transmitted diseases clinic; 99 women had lower genital tract infection and 56 had Chlamydia-associated pelvic inflammatory disease (PID). In the group with lower genital tract infection, women with serovar F differed from those with serovars of class B or C in that they exhibited fewer signs of cervical infection, including easily induced bleeding (P = .04), edema of the zone of cervical ectopy (P = .06), and colposcopic evidence of mucopurulent endocervical discharge (P = .007). Serovar F also produced fewer infections with inclusion counts of > or = 1,000 and fewer rectal infections (P = .04). There was no apparent association of any specific serovar with PID. Thus, in this population, serovar F was associated with fewer objective clinical manifestations of mucopurulent endocervical discharge, and the distribution of chlamydial serovars found in PID reflected that found in lower genital tract infection.