OBJECTIVE To describe the syndrome of rhabdomyolysis during bacterial sepsis with regard to incidence, blood bacteriology and complications and to examine the association between hyperosmolal state and rhabdomyolysis, evaluating the relationship between plasma osmolality (Posm) and serum creatine phosphokinase (CPK) levels. METHODS Prospective study including all patients admitted to the intensive care unit (ICU) for sepsis with positive blood culture and rhabdomyolysis over a 3-year period. METHODS Seven-bed medical/surgical ICU of a teaching hospital. METHODS 35 patients (group 1) with bacterial sepsis-induced rhabdomyolysis (15 males, 20 females; mean age 71+/-13 years) and 122 (group 2) bacteraemic septic patients without rhabdomyolysis (49 males, 73 females; mean age 68+/-15) were studied. Patients with rhabdomyolysis were divided into gram(+) and gram(-) subgroups according to the blood culture growth. RESULTS From 491 patients recorded, 35 fulfilled the inclusion criteria for bacterial sepsis-induced rhabdomyolysis (7.1%). Gram-positive bacteria predominated in group 1 (69%), while gram-negative predominated (60%) in group 2. There was a correlation between CPK and Posm levels in the rhabdomyolysis Group (r = 0.52, R2 = 0.27, p = 0.003). There was a stronger correlation between these two variables (r = 0.67, R2 = 0.45, p = 0.001) in the gram(+).subgroup. Acute renal failure (68.5%) and electrolyte disorders such as hyperkalaemia (34%) and hypocalcaemia (48.5%) were the major complications in the rhabdomyolysis group. Sixteen (45.7%) patients in group 1 and 49 (40%) in group 2 died during their stay in the ICU from sepsis and multiple organ failure. Rhabdomyolysis was not considered a contributing factor to their death, as none of our patients died during or immediately after the syndrome. CONCLUSIONS Bacterial sepsis-induced rhabdomyolysis results from certain types of microorganisms, mainly gram-positive and to a lesser extent gram-negative. Hyperosmolality is a predisposing mechanism for rhabdomyolysis during bacteraemic sepsis from any type of bacterial microorganism.