We treated nine patients of mycoplasmal pneumonia with sparfloxacin (SPFX) the clinical efficacy, safety and usefulness of SPFX were evaluated. SPFX was administered orally at doses of 200 or 300 mg once daily, and we performed bronchoalveolar lavage (BAL) examinations in five patients. BAL was performed 5 hours after oral administration of 100 mg in one case, 19 hours after oral administration of 200 mg in four cases. Concentrations of SPFX and alubumine were measured in serum and in BALF (bronchoalveolar lavage fluid). The following results were obtained. 1. Nine patients were evaluated; eight patients judged as Good, one patient as Excellent. 2. The serum and BALF levels of SPFX was 0.79 microgram/ml, 0.107 microgram/ml 5 hours after single oral administration of 100 mg in one case and 19 hours after oral administration of 200 mg in four cases, those of levels of SPFX were 0.835 +/- 0.274 microgram/ml and 0.081 +/- 0.033 microgram/ml, respectively. 3. The ratio of SPFX/albumin in BALF was significantly higher than in the serum. From these results, we consider that SPFX is a useful antimicrobial agent for mycoplasmal pneumonia.