The diagnostic sensitivity of the numbers of leukocytes in the sediment of first-voided urine and in gram-stained smears of urethral secretions was evaluated by a study of 62 men with symptoms of nongonococcal urethritis. Fifty-one patients (82.3%) had pyuria (defined as ten or more leukocytes per high-power field) in the sediment of first-voided urine, whereas 8 (45.2%) had more than four leukocytes per oil-immersion held in gram-stained urethral smears. Frequencies of positive first-voided urine sediments and urethral smears were similar in Chlamydia trachomatis--positive and -negative cases. Results of cultures, urinalyses, and urethral smears were not affected by recent micturition. Pyuria in the first-voided urine but not a positive urethral smear is a sensitive sign of urethritis whether or not urethral discharge is evident. Specimens of urethral secretions were subjected to different storage conditions to determine the effect on subsequent isolation of C. trachomatis. Equal rates of isolation were demonstrated for specimens that had been held at 4 degrees C for either four or 20-24 hr or frozen to -70 degrees C for one week prior to culture.