OBJECTIVES To estimate the risk of death and examine the predictors of death and virological/immunological response, following diagnosis of multidrug-resistant (MDR) HIV-1 in a UK multicentre cohort of HIV-infected individuals. METHODS Five hundred and seventy-two patients were identified with MDR HIV-1 between 1997 and 2004. Factors associated with survival and virological/immunological response 24-48 weeks after MDR diagnosis were determined by the Poisson and linear regression, respectively. RESULTS Patient characteristics: 86% males; median age 39 years; median CD4 and viral load (VL) at MDR diagnosis 230 cells/mm3 and 4.2 log10 copies/mL; median number of antiretroviral drugs previously exposed to 8. Sixty patients died over a median follow-up of 31 months (IQR: 17-50), giving an estimated mortality rate of 3.7 deaths per 100 person-years (95% CI 2.9-4.7) following MDR diagnosis. In adjusted analysis, higher CD4 count, lower VL, more recent calendar year, lower number of antiretroviral drugs previously exposed to and greater age at MDR diagnosis were associated with an increased chance of survival. There was some evidence of a better virological response at 24-48 weeks after MDR diagnosis in patients who changed regimen compared with patients who did not change regimen. CONCLUSIONS The risk of death following MDR diagnosis may be at least 3-fold the risk observed overall in HIV-infected individuals. Changing antiretroviral therapy following emergence of MDR HIV-1 may be associated with improved short-term virological response.