Nimodipine is used parenterally to treat ischemic neurological deficits caused by subarachnoid haemorraghe. Infusion of nimodipine should be continued during anaesthesia, surgery or angiography. In this context a simultaneous administration of nimodipine, propofol and fentanyl or remifentanil could be of great advantage. So the aim of this study was to evaluate the physical stability (droplet size) of propofol emulsions in combination with nimodipine and fentanyl/remifentanil. Droplet size of intravenous emulsions is of particular relevance as the administration of larger droplets to patients may cause pulmonary embolism. So the number of oil droplets > 10 microm was determined in combinations of propofol emulsion with nimodipine and fentanyl/remifentanil immediately after mixing and after 20 hours by using microscopy. The experiments showed that all combinations of propofol (1 and 2%) with nimodipine infusion solution resulted in coalescence of oil droplets, which finally caused a visible phase separation. Macrogol (polyethylene glycol 400) was identified as the component in nimodipine infusion solution which induced the physicochemical incompatibility with propofol lipid emulsions.