Efficacy and tolerability of flurithromycin ethylsuccinate were evaluated in lower respiratory tract infections. One hundred and ten patients (38 women, 72 men; age range 18-87 years) were treated with on 375 mg tablet 12-hourly for a mean duration of 8.7 days. One hundred and five patients were evaluable for efficacy. Overall clinical cure rate was 62.9%; improvement was recorded in 19% of patients for a total satisfactory clinical response rate of 81.9%. Sputum production decreased in most patients, being absent after treatment in 47% (only one patient was negative at baseline); sputum was purulent or mucopurulent in 80% of subjects before and in 20% after treatment. Bacteriological evaluation was possible in 72 patients: pathogen eradication was achieved in 80.2% of cases. Eight patients out of 110 reported adverse reactions, mainly gastrointestinal; in one case treatment had to be discontinued. These results demonstrate that flurithromycin ethylsuccinate is safe and effective in the treatment of lower respiratory tract infections.