Between January 1993 and February 1993, the left internal thoracic arteries of 40 consecutive patients scheduled for aortocoronary bypass operation were examined by transthoracic B-mode imaging. Perioperative measurements correlated well with preoperative noninvasive measurements (r = 0.914). In the postoperative period, B-mode images could not be obtained in 17 (44.7%) of 38 patients. Adequate Doppler spectra of the internal thoracic artery were obtained in all patients preoperatively and in 36 (94.7%) of 38 patients postoperatively. Preoperatively a triphasic wave form was obtained with a large systolic peak followed by small reversed and diastolic components in all patients. Postoperatively this triphasic wave form had been converted into a combined systolic-diastolic wave form. In all patients peak systolic velocity of the internal thoracic artery decreased (96.4 +/- 15.3 vs 64.2 +/- 18.9 cm/sec., P < 0.05), and peak diastolic velocity increased (21.7 +/- 8.8 vs 28.3 +/- 11.2 cm/sec., P < 0.05) significantly in the postoperative period as compared with the preoperative values. A slight decrease in peak systolic and diastolic velocities was detected at twelve months postoperatively. This study indicates that transthoracic B-mode imaging and Doppler spectrum analysis are reliable techniques in the preoperative and postoperative assessment of the internal thoracic artery in myocardial revascularization.