Two forms of treatment of acute pulmonary exacerbations in patients with cystic fibrosis were compared: intravenous ticarcillin (300 mg drug per kg per day) and tobramycin (10 mg drug per kg per day) versus the same intravenous antibiotic therapy plus inhaled tobramycin (80 mg three times per day). The 16 patients in the intravenous plus inhaled tobramycin group were similar to the 12 control patients in age, sex, Schwachman scores, pulmonary function and pretreatment colony counts of Pseudomonas aeruginosa in sputum. Treatment resulted in significant improvement in clinical status and pulmonary function without any apparent differences in the two groups. However, intravenous plus inhaled tobramycin resulted in temporary eradication of P. aeruginosa in 63% of the patients compared to 25% in the intravenous only group (P = 0.03). Suppression of P. aeruginosa in sputum cultures did not correlate with clinical response to treatment. No renal toxicity or elevations of serum tobramycin were observed in the intravenous plus inhaled tobramycin group.