Summary The benefit of peritoneal lavage in the treatment of intra-abdominal infection and sepsis has not been established in an evidence-based way yet. Nevertheless it is widely practised depending on the surgeon’s personal view and local guidelines. In contrast to lavage, the administration of G-CSF as a new therapeutic option, which stimulates the immune system, has not been used in clinical therapy yet, although the results of experimental and clinical trials have been promising. To simulate the conditions of clinical sepsis as accurately as possible, the CMRT-Concept (clinical modelling randomized trial) has been developed. The CMRTs contain important clinical elements such as: anaesthesia, antibiotics, volume substitution, laparotomy, contamination and infection with standardized human stool bacteria and analgesia. In addition to clinical elements they also contain many features of randomized, clinical trials like: number needed to treat, randomization, blinding procedures and flow charts as postulated in the CONSORT Statement. Three independent CMRTs have been conducted for this paper: 1) Peritoneal lavage with physiological saline solution versus lavage with the bacteriostatic agent taurolidine. 2) No lavage versus lavage with saline solution versus lavage with adjuvant administration of G-CSF 12 h before PCI and 12 h plus 36 h afterwards. 3) No lavage versus peritoneal lavage. The number of animals in each group has been increased from 18 to 30 based on statistical calculations. In Trial 1 lavage with taurolidine was not superior compared to lavage with normal saline solution. 5 of 18 animals survived the end of the trial (120 h) in the taurolidine group, 8 animals survived in the saline group. In Trial 2 most animals survived in the G-CSF treatment group (11 animals) compared to 6 animals in the control-group with no lavage and 3 animals in the lavage group. Phagocytic activity 1h after PCI was increased, due to G-CSF administration, IL-6 and TNF-α-levels in peritoneal-fluid were decreased and IL-6 and IL-10-levels in plasma also were decreased. In trial 3 no significant difference in survival rate was observed. Without lavage 19 animals survived compared to 14 animals with lavage.