The clinical presentation of plantar fasciitis may be mimicked by a number of other painful heel conditions. Thus, magnetic resonance (MR) imaging was used to develop objective morphologic criteria to establish a diagnosis of plantar fasciitis in eight patients. Sagittal T1-weighted and coronal intermediate and T2-weighted images of symptomatic and asymptomatic feet were obtained; additional sequences were used for symptomatic feet. Maximum thickness of the plantar fascia was significantly increased (P less than .0001) in patients with plantar fasciitis (sagittal, 7.40 mm +/- 1.17, and coronal, 7.56 mm +/- 1.01) compared with age- and sex-matched volunteers (sagittal, 3.22 mm +/- 0.44, and coronal, 3.44 mm +/- 0.53) and young male controls (sagittal, 3.00 mm +/- 0.8, and coronal, 3.00 mm +/- 0.0). Furthermore, nine of 10 feet with plantar fasciitis had areas of moderately increased signal intensity in the substance of the fascia. MR imaging may provide an objective assessment of the morphologic changes associated with plantar fasciitis, as well as assist in excluding other causes of heel pain.