We analyzed retrospectively the illnesses of 82 patients with Campylobacter jejuni enteritis to ascertain the efficacy of antimicrobials and drugs that inhibit gastrointestinal motility. Forty-four patients were treated with only supportive measures consisting of diet modification and fluids; 22 others received an antimotility agent for at least 48 h; the remaining 16 were given an antimicrobial at or near the time of therapeutic intervention. The three groups were similar in terms of severity of symptoms and signs. There was a greater need for secondary antimicrobial therapy because of static or worsening illness in the group treated with antimotility agents (8/22, 36%) than in the others (4/44,9%; 2/16, 13%: p less than 0.02). Furthermore, six patients treated initially and 10 treated secondarily with erythromycin or tetracycline had illnesses of shorter duration than did untreated controls paired by age, sex, length and severity of symptoms and signs, hematochezia, and antimotility therapy (p less than 0.05). Thus treatment of C. jejuni enteritis with erythromycin or a tetracycline shortened the illness, but antimotility agents impeded the resolution of the infection.