Although numerous clinical, laboratory, and pharmacological variables have been reported as significant risk factors for critical illness polyneuromyopathy (CIPM), there is still no consensus on the aetiology of this condition. Objectives of the study were to assess the clinical and electrophysiological incidence and risk factors for CIPM.A cohort of critically ill patients was observed prospectively for a one-month period and the association between neuromuscular involvement and various potential risk factors was evaluated. Sixty one critically ill patients completed the follow-up (30 women, 31 men, median age 59 years).CIPM development was detected clinically in 17 patients (27.9 %) and electrophysiologically in 35 patients (57.4 %). CIPM was significantly associated with the presence and duration of systemic inflammatory response syndrome and the severity of multiple, respiratory, central nervous, and cardiovascular organ failures. The median duration of mechanical ventilation was significantly longer in patients with CIPM than in those without (16 vs 3 days, p<0.001). Independent predictors of CIPM obtainable within the 1(st) week of critical illness were the admission sequential organ failure assessment score (odds ratio [OR], 1.15; 95% confidence interval [CI], 1.02-1.36), the 1(st) week total sequential organ failure assessment scores (OR, 1.14; 95 % CI, 1.06-1.46) and the 1(st) week duration of systemic inflammatory response syndrome (OR, 1.05; 95% CI, 1.01-1.15). They were able to correctly predict the development of CIPM at the end of the 1(st) week in about 80% of critically ill cases.In conclusion, the presence and duration of systemic inflammatory response syndrome and the severity of multiple and several organ failures are associated with increased risk of the development of CIPM.