Extended-spectrum betalactamases (ESBLs) are enzymes produced by gram-negative bacteria which are capable of destroying the betalactamic ring of third-generation cephalosporins enabling the bacteria to continue the peptido­ glican crosslinking process resulting in uilaltered integrity of the bacteria! cell wall. ESBLs were first detected in the 1980s. Its incidence increased and dissemination in all continents has lead to greater morbidity and mortality rates, prolonged hospitalization, greater usage of carbapenems and rising health care costs. Prediction of resistance patterns of infecting microorganisms based on the analysis of the risk factors associated facilitate optimal selection of empirical autibiotic treatment, rationalized use of available broad spectrum antibiotics and improvement of patient survival. This review searched for case studies and follow up trials which investigated the risk factors associated with ESBL producing bacterial infection or colonization, that is, previous exposure to antibiotics, hospitalization at the ICU, urinary catheterization, central venous catheterization and mechanical ventilation.