Background: Liver biopsy is an invasive technique with associated major complications. There is no information on the validity of five non-invasive indexes based on routinely available parameters, estimated and validated in hepatitis C virus (HCV) monoinfected patients, in human immuno-deficiency virus (HIV)/HCV coinfected patients. Aim: To validate these predictive models of liver fibrosis in HIV/HCV coinfected patients. Patients: A total of 357 (90% ) of 398 patients from five hospitals were investigated, who underwent liver biopsy and who had complete data to validate all of the models considered. Methods: The predictive accuracy of the indexes was tested by measuring areas under the receiver operating characteristic curves. Diagnostic accuracy was calculated by estimating sensitivity, specificity, and positive (PPV) and negative (NPV)- predictive values. Results: The models performed better when liver biopsies ≥ 15 mm were used as reference. In this setting, the Forns and Wai indexes, models aimed at discriminating significant fibrosis, showed PPV of 94% and 87% , respectively. Using these models, 27- 34% of patients could benefit from exclusion of liver biopsy. If both models were applied sequentially, 41% of liver biopsies could be spared. The indexes aimed at predicting cirrhosis achieved NPV of up to 100% . However, they showed very low PPV. Conclusions: The diagnostic accuracy of thesemodelswas lower in HIV/HCV coinfected patients than in the validation studies performed in HCV monoinfected patients. However, simple fibrosis tests may render liver biopsy unnecessary in deciding anti-HCV treatment in over one third of patients with HIV infection and chronic hepatitis C. Background: Liver biopsy is an invasive technique with associated major complications. There is no information on the validity of five non-invasive indexes based on routinely available parameters, estimated and validated in hepatitis C virus (HCV) monoinfected patients, in human immuno-deficiency Virus: HIV / HCV coinfected patients. Aim: To validate these predictive models of liver fibrosis in HIV / HCV coinfected patients. Patients: A total of 357 (90%) of 398 patients from five hospitals were investigated, who underwent liver biopsy and who had complete data to validate all of the models considered. Methods: The predictive accuracy of the indexes was tested by measuring areas under the receiver operating characteristic curves. Diagnostic accuracy was calculated by estimating sensitivity, specificity, and positive (PPV) and negative NPV) - predictive values. Results: The models performed better when liver biopsies ≥ 15 mm were used as reference. In this setting, the Forns and Wai ind The use of these models, 27-34% of patients could benefit from exclusion of liver biopsy. If both models were applied sequentially, 41% of liver biopsies However, they showed very low PPV. Conclusions: The diagnostic accuracy of these patterns was lower in HIV / HCV coinfected patients than in the validation studies performed in HCV monoinfected patients However, simple fibrosis tests may render liver biopsy unnecessary in deciding anti-HCV treatment in over one third of patients with HIV infection and chronic hepatitis C