The aim of this study was to evaluate whether an insufficient flow of information from the primary to the secondary sector was the cause of unnecessary duplications of investigations. From practitioners of 202 patients admitted to a medical department information about paraclinical examinations during the previous year was obtained. In all 111 general practitioners participated. An average of 3.0 blood analyses and 0.9 other investigations were carried out on each patient. 44% of the patients were not investigated at all. An average of 1.9 blood analyses and 0.2 other investigations on each patient were repeated. 22% of the repetitions in both cases were due to insufficient communication between the practitioner and the hospital. These figures seem low and insufficient communication between the primary and the secondary sector appears to be a minor problem.