The treatment of community-acquired pneumonia is empirical in most cases and must cover a wide range of potential pathogens, such as Streptococcus pneumoniae, including penicillin-resistant strains, Haemophilus influenzae and intracellular microorganisms. The objective of this double-blind, randomized, parallel group study was to compare the efficacy and safety of sparfloxacin (400 mg loading dose, followed by 200 mg o.d.) with that of oral amoxycillin-clavulanic acid (500/125 mg t.i.d.) or oral erythromycin (1 g b.i.d.), during 7-14 days in 808 patients with confirmed community-acquired pneumonia. The overall success rates for sparfloxacin (87%), amoxycillin-clavulanic acid (80%) and erythromycin (85%) were similar in evaluable patients, and the equivalence hypothesis used for the statistical analysis showed at least an equivalent efficacy for the three antibiotics tested. The analysis of microbiologically documented infections (40% of the patients) showed that overall success rates were similar for S. pneumoniae and H. influenzae infections. Treatment withdrawal was necessary in 3.5, 2.5 and 7.7% of the patients treated with sparfloxacin, amoxycillin-clavulanic acid and erythromycin, respectively. This study indicates that sparfloxacin was at least as effective as amoxycillin-clavulanic acid or erythromycin in the treatment of mild-to-moderate community-acquired pneumonia and that the adverse effects were similar in the three groups.