The effect of therapeutic ultrasound on the formation of new blood vessels in full-thickness excised lesions in the flank skin of adult rats was assessed quantitatively using microfocal x-ray techniques. Wounds were either sham-treated (control group) or exposed to ultrasound for 5 min daily at an intensity of 0.1 W/cm2 SATA (frequency either 0.75 MHz or 3.0 MHz). By 5 days after injury there were more blood vessels in equivalent regions of the granulation tissue of the ultrasound-treated wounds than in the control wounds. This suggested that the ultrasound-treated wounds were at a more advanced stage in the repair process. By 7 days after injury there was no significant difference in blood vessel number between the three groups.