The correlation of histopathologic findings with duplex Doppler sonography (DDS) in 24 biopsies in 21 patients was studied. The resistive indices (RI) of the acute rejection group were statistically different (p = .04) from those that were negative for rejection or clinical controls. Although the number of cases of moderate to severe interstitial and/or vascular rejection was relatively small compared to the mild group, patients with the more severe forms of rejection (moderate to severe interstitial with or without vascular rejection) tended to have higher RIs (.89 +/- .04) than those with the milder forms of rejection (.75 +/- .05).