Acute lower respiratory tract infection is the most common condition treated in primary care. Many physicians still prescribe antibiotics; however, systematic reviews of the use of antibiotics are small and have diverse conclusions. To estimate the effectiveness of 3 prescribing strategies and an information leaflet for acute lower respiratory tract infection. A randomized controlled trial conducted from August 18, 1998, to July 30, 2003, of 807 patients presenting in a primary care setting with acute uncomplicated lower respiratory tract infection. Patients were assigned to 1 of 6 groups by a factorial design: leaflet or no leaflet and 1 of 3 antibiotic groups (immediate antibiotics, no offer of antibiotics, and delayed antibiotics). Three strategies, immediate antibiotics (n = 262), a delayed antibiotic prescription (n = 272), and no offer of antibiotics (n = 273), were prescribed. Approximately half of each group received an information leaflet (129 for immediate antibiotics, 136 for delayed antibiotic prescription, and 140 for no antibiotics). Symptom duration and severity. A total of 562 patients (70%) returned complete diaries and 78 (10%) provided information about both symptom duration and severity. Cough rated at least "a slight problem" lasted a mean of 11.7 days (25% of patients had a cough lasting > or =17 days). An information leaflet had no effect on the main outcomes. Compared with no offer of antibiotics, other strategies did not alter cough duration (delayed, 0.75 days; 95% confidence intervals [CI], -0.37 to 1.88; immediate, 0.11 days; 95% CI, -1.01 to 1.24) or other primary outcomes. Compared with the immediate antibiotic group, slightly fewer patients in the delayed and control groups used antibiotics (96%, 20%, and 16%, respectively; P<.001), fewer patients were "very satisfied" (86%, 77%, and 72%, respectively; P = .005), and fewer patients believed in the effectiveness of antibiotics (75%, 40%, and 47%, respectively; P<.001). There were lower reattendances within a month with antibiotics (mean attendances for no antibiotics, 0.19; delayed, 0.12; and immediate, 0.11; P = .04) and higher attendance with a leaflet (mean attendances for no leaflet, 0.11; and leaflet, 0.17; P = .02). No offer or a delayed offer of antibiotics for acute uncomplicated lower respiratory tract infection is acceptable, associated with little difference in symptom resolution, and is likely to considerably reduce antibiotic use and beliefs in the effectiveness of antibiotics.