This first German prevalence study surveilling nosocomial wound infections (NWI) was carried out in 72 representatively selected hospitals. NWI were recorded by 4 validated investigators. Seventy-nine NWI were recorded among 4983 operated patients (prevalence rate: 1.61%), most of them after amputation of limbs (6.1%) and operations on the colon or rectum (3.1%). The 3 risk factors from the NNIS (National Nosocomial Infection Surveillance) index for postoperative wound infections were for the first time applied in this prevalence study. Patients with contaminated wounds had significantly more wound infections (P=0.01, likelihood ratio test) whereas, in contrast to the NNIS index, patients with ASA score >3 (P= 0.07) or long lasting operations (>75th percentile) did not (P=0.1). Therefore, for the stratification of NWI rates wound contamination is the single most important factor.