Background: Plain radiography, subtraction arthrography, nuclear arthrography, and bone scintigraphy are imaging techniques commonly used to identify aseptic femoral component loosening. Controversy exists about the relative utility of these techniques. Patients and methods: W e evaluated the diagnostic accuracy and interobserver reliability of the four techniques in 78 consecutive patients (mean age 70 years, range 29-88 years) referred for evaluation of their femoral hip prostheses. The standard evaluation protocol consisted of plain radiography followed by subtraction arthrography, nuclear arthrography, and bone scintigraphy. Surgery or the subsequent clinical course of the patient was used as gold standard. Results: Over all, plain radiography had a sensitivity and specificity of 81 and 74%, respectively. Subtraction arthrography had a sensitivity of 47% and a specificity of 78%. Nuclear arthrography had a sensitivity of 69% and a specificity of 76%, and bone scintigraphy had a sensitivity of 88% with a specificity of 50%. Conclusion: We found considerable int erobserver variability in all four techniques. Multivariate regression analysis revealed that bone scintigraphy and nuclear arthrography together made a significant contribution to the diagnosis when used in combination with plain radiography and are, when plain radiography is inconclusive, useful additional diagnostic techniques for the detection of femoral component loosening.