The bioavailability of ofloxacin in tonsil tissue, after a single oral dose of 200 mg 2 h before surgery, was evaluated in 14 patients undergoing tonsillectomy for recurrent or chronic infection. A blood specimen was obtained just before drug administration and at the time of tonsillectomy, together with a specimen of tonsil tissue. The mean values of the serum and tonsil concentrations 2 h after a single dose of 200 mg were 1.17 mg/l +/- 0.47 and 1.61 mg/l +/- 0.62 respectively with a mean tonsil/serum ratio of 1.40 +/- 0.19. These values indicate good penetration of ofloxacin into tonsil tissue. No clinical or biological side-effects were observed.