BACKGROUND: Whooping cough is a highly contagious disease. Infants are the population at highest risk of severe disease and death. Erythromycin for 14 days is recommended for treatment and contact prophylaxis but this regime is considered inconvenient and prolonged. The value of contact prophylaxis is uncertain. OBJECTIVES: To study the benefits and risks of antibiotic treatment of and contact prophylaxis against whooping cough. SEARCH STRATEGY: The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 1, 2004); MEDLINE (January 1966 to February 2004); EMBASE (January 1974 to August 2003); conference abstracts and reference lists of articles were searched. Study investigators and pharmaceutical companies were approached for additional information (published or unpublished studies). There were no constraints based on language or publication status. SELECTION CRITERIA: All randomised and quasi-randomised controlled trials of antibiotics for treatment of and contact prophylaxis against whooping cough were included in the systematic review. DATA COLLECTION AND ANALYSIS: At least three reviewers independently extracted data and assessed the quality of each trial. MAIN RESULTS: Twelve trials with 1,720 participants met the inclusion criteria. Ten trials investigated treatment regimens and two investigated prophylaxis regimens. The quality of the trials was variable. Results showed that short-term antibiotics (azithromycin for three days, clarithromycin for seven days, or erythromycin estolate for seven days) were equally effective with long-term antibiotic treatment (erythromycin estolate or erythromycin for 14 days) in the microbiological eradication of Bordetella pertussis (B. pertussis) from the nasopharynx. The relative risk (RR) was 1.02 (95% confidence interval (CI) 0.98 to 1.05). Side effects were fewer with short-term treatment (RR 0.66; 95% CI 0.52 to 0.83). There were no differences in clinical improvement or microbiological relapse between short and long-term treatment regimens. Contact prophylaxis (of contacts older than six months of age) with antibiotics did not significantly improve clinical symptoms or the number of cases that developed culture positive B. pertussis. AUTHORS' CONCLUSIONS: Antibiotics are effective in eliminating B. pertussis from patients with the disease, rendering them non-infectious, but do not alter the subsequent clinical course of the illness. Effective regimens include: three days of azithromycin, seven days of clarithromycin, seven or 14 days of erythromycin estolate, and 14 days of erythromycin ethylsuccinate. Considering microbiological clearance and side effects, three days of azithromycin or seven days of clarithromycin are the best regimens. Seven days of trimethoprim/sulfamethoxazole also appeared to be effective for the eradication of B. pertussis from the nasopharynx and may serve as an alternative antibiotic treatment for patients who cannot tolerate a macrolide. There is insufficient evidence to determine the benefit of prophylactic treatment of pertussis contacts.