OBJECTIVES: The aim of our study was to investigate the circadian and weekly variation and assess the influence of environmental variables on the occurrence of acute myocardial infarction (AMI). METHODS: Our study population consisted of 2983 consecutive patients admitted with AMI between January 2006 and May 2008. Data were abstracted from hospital records and partially from an electronic database. In patients with a known time of onset of AMI, circadian variation was analysed. In all patients, weekly variation of onset of AMI was analysed. Information on daily mean temperature, sunny hours, rainy hours, maximal humidity and mean atmospheric pressure was obtained from the KNMI database and the influence of these environmental variables on the incidence of AMI was analysed. RESULTS AND CONCLUSION: Incidence of AMI shows a circadian pattern with an increase in occurrence during daylight. AMI occurs equally on each day of the week and no relation was found between environmental variables and the occurrence of AMI.