The diagnosis of a prosthetic joint infection is difficult, but crucial for appropriate treatment. Scintigraphy with specific markers for infection (labelled white cells or immunoglobulin-G) has been reported as a more reliable diagnostic tool than clinical assessment (fever, fistula), laboratory studies (polynuclear neutrophil count, erythrocyte rate sedimentation, and C-reactive protein), and preoperative aspiration. In the first part of this study, we retrospectively reviewed 230 patients admitted with a suspected prosthetic joint infection, and examined the validity of the different diagnostic tools for the group as a whole and for subgroups according to the Coventry classification. In the second part, we reviewed 35 articles about preoperative evaluation of infection in prosthetic joints and compared them to our findings. Our study indicates that C-reactive protein and joint aspiration are the most useful tools to diagnose prosthetic joint infection even in situations of chronic infection (Coventry type II).