OBJECTIVE: To know the clinically meaningful findings of ultrasonography in plantar fasciitis. METHOD: Thirty one feet of 24 patients who had clinical diagnosis of plantar fasciitis and 70 feet of 35 healthy volunteers were evaluated with ultrasound. Sagittal sonograms were obtained in the prone position, and the plantar fascia thickness (PFT) was measured at proximal end near its insertion into the calcaneus. Hypoechogenecity, perifascial fluid collection, tendon rupture, calcaneal spur and calcification were also evaluated. RESULTS: The plantar fascia thickness (PFT) of the symptomatic heels (SH) of patients group (4.83+/-0.86 mm) was significantly greater than that of their asymtomatic heels (ASH) (2.95+/-0.57 mm)(p<0.05) and it was also greater than that of control group (2.63+/-0.41 mm)(p<0.05). The range of difference of both PFT was 0.7~3.2 mm in patients group and 0~0.8 mm in control group. Hypoechogenecity was found in 22 SH (71%), perifascial fluid collection in 5 SH (16%) and calcification in 2 SH (6%). Calcaneal bony spur was identified in 7 SH (26%) on simple radiography. CONCLUSION: Increased thickness (>3.8 mm), difference of thickness between SH and ASH (>1.0 mm) and hypoecho genecity of plantar fascia were clinically meaningful ultrasonographic findings of plantar fasciitis, and ultrasonogrphy can be used as the inital imaging modality for the diagnosis.