We created a clinical prediction rule to identify patients at risk of invasive candidiasis (IC) in the intensive care unit (ICU) (Eur J Clin Microbiol Infect Dis 2007; 26:271). The rule applies to <10% of patients in ICUs. We sought to create a more inclusive rule for clinical trials. Retrospective review of patients admitted to ICU ≥ 4 days, collecting risk factors and outcomes. Variations of the rule based on introduction of mechanical ventilation and risk factors were assessed. We reviewed 597 patients with a mean APACHE II score of 14.4, mean ICU stay of 12.5 days and mean ventilation time of 10.7 days. A variation of the rule requiring mechanical ventilation AND central venous catheter AND broad spectrum antibiotics on days 1-3 AND an additional risk factor applied to 18% of patients, maintaining the incidence of IC at 10%. Modification of our original rule resulted in a more inclusive rule for studies. © 2009 Blackwell Verlag GmbH.