OBJECTIVES: DUET-1 and DUET-2 are two identically designed, randomized, double-blind, placebo-controlled, Phase-III-trials, which have demonstrated superiority of etravirine (ETR)+ background regimen (BR) (ETR-arm) versus placebo+BR (PLAC-arm) in HIV-1-infected, treatment-experienced patients. Hospitalisation events and duration of hospital stay were recorded for each patient.  The objective of this study was to calculate the costs of hospitalisations observed in the DUET trials for the German healthcare setting. METHODS: The number and duration of hospitalisations were analyzed at 48 weeks. Hospitalisation rates were analyzed by negative binomial regression. Hospital costs in the German setting were calculated by applying the German-DRG system for each patient based on individually recorded disease characteristics and diagnoses.  For all psychiatric admissions, where DRGs are not applicable, the fixed daily rate was used (€241/d). RESULTS: A total of 1203 patients were included: 599 vs 604 in the ETR- versus PLAC-arms. Numbers (%) of patients hospitalised were 105 (17.5%) vs. 139 (23.0%) for ETR-arm vs. PLAC-arm, respectively (p=0.0006). The mean durations of stays for second (13.5d) or subsequent hospitalisations (15.6d) were longer than for first admission (10.4d) overall, and for all stays were longer and therefore more expensive in PLAC-arm (12.3d) vs. ETR-arm (11.0d). Patients with baseline-CD4-cell-counts of <50 cells/mm3 had a statistically significant lower hospitalisation rate in the ETR-arm versus PLAC-arm (p=0.0001). Total hospital days observed during the 48-week follow-up period were 1702 vs. 2747 for ETR-arm vs. PLAC-arm. Calculated total hospital costs were €633.238 (ETR-arm) vs. €975,750 (PLAC-arm), resulting in a mean saving for hospitalisation costs of €572 for each patient treated within the ETR-arm. CONCLUSIONS: At Week 48, ETR+BR provided a statistically significant reduction in overall hospitalisations rates and costs versus placebo+BR. Reductions in hospitalisation time indicate significant savings to the healthcare system and clinical benefit to the patients.