The number of dispensing errors occurring in hospital pharmacy and being detectable by inspection was studied by simple statistical method. Errors in calculation occurred most frequently. They often occurred 1) when new graduates are employed; 2) after vacation; 3) when places of vials of powder medicines are changed; 4) through carelessness; 5) in confusion of one drug with another with similar name. Errors in confusion of the product names were analyzed by Pragnanz theory by Max Weltheimer. The names containing 4-7 common alphabetic letters most often caused confusion. Also, names with 1-3 common first letters were confused most frequently.