Recently, the number of physicians using Kampo (Japanese traditional herbal) medicines has been increasing in Japan, and it is becoming more common for pharmacists to dispense Kampo medicines. As Kampo medicines become more popular, in addition to extract formulae, the use of decocting formulae that are more suited to each patient's predisposition and symptoms has increased. Therefore, more pharmacists are dispensing such decocting formulae. However, dispensing decocting formulae can be a complicated task. The risk of dispensing errors is not small. In present paper, we examined preventive measures based on investigations of errors involving decocting formulae in our Kampo clinic. From 1990 to 1999, there were 54 cases in which errors were found after patients received their medicines, and 44 of these cases were dispensing errors. To prevent such errors, in addition to having the knowledge of Kampo medicine and medicinal herbs that is needed for dispensing decocting formulae, it is also necessary to understand the contents of the prescription. The most important preventive measures are to re-inspect the weight and contents of the prescription after preparing it, and to do a final inspection of the medicine contents with the patient. It is expected that this report will play a role in preventing dispensing errors of Kampo medicines by pharmacists.