We examined the prevalence of Chlamydia trachomatis in the cervix and the fallopian tubes of patients with acute salpingitis. Cycloheximide-treated McCoy cells were used as the growth medium. For purposes of comparison, women with infections confined to the lower genital tract and women without signs of genital infections were also studied. C. trachomatis was isolated from the cervix in 19 of 53 patients with acute salpingitis, in one of 18 lower-genital-tract infections and in none of 12 without signs of genital infection. C. trachomatis was recovered from six of the 20 valid specimens from the fallopian tubes of the patients with acute salpingitis. Our results indicate that chlamydia is a common etiologic agent in acute salpingitis.