Combined contrast and radionuclide arthrography was performed in 71 cemented, non-cemented and hybrid hip arthroplasties for diagnosis of component loosening. In 31 cases, either one or two prosthesis components were clearly loose upon clinical and radiological diagnosis, with subsequent intraoperative confirmation. The other 40 cases had doubtful component loosening, with discrepancy between clinical and radiological findings, and were investigated for clarification. Contrast and radionuclide arthrograms were compared with sequential plain radiographs and their ability to indicate component loosening was evaluated. The combined contrast and radionuclide arthrograms proved in 90.9% of the cases whether a loose component existed as confirmed by intraoperative findings. They had a high sensitivity, specificity and predictive accuracy for both the acetabular and the femoral component. Sensitivity and predictive accuracy were remarkably precise in comparison to those of plain radiographs on the acetabular side. In nearly all patients with contradictory clinical and radiological findings, conclusive diagnosis was possible on the basis of the contrast and radionuclide arthrograms. Coinciding positive results in both contrast and radionuclide arthrograms were verified in each operated case. The combination of contrast and radionuclide arthrography is an useful method to diagnose doubtful loosening of hip arthroplasty components, especially in addition to routine sequential plain radiographs.