In line with the trend of expanding the capabilities of clinical laboratories, the blood-drawing operations are transferred to the clinical laboratories in many hospitals in Japan. In our hospital, the blood-drawing section accompanied by a satellite laboratory is located near the outpatient clinic. Since 2000, the Division of Clinical Laboratories began assisting the blood-drawing operations. Among several problems related to a blood drawing, the patients' waiting time for blood-drawing was one of the most serious problems. The definition of a patient's waiting time is from reception to the physical blood drawing. The number of patients and the number of personnel available for blood drawings were analyzed by the differences of time of day and day of the week. These analyses prompted us to introduce the "on-demand helper system" to this particular section. The introduction of this "on-demand helper system" made it possible to dramatically reduce the patients' waiting time for a blood-drawing. Although the situation of a blood-drawing operation would differ from hospital to hospital, our introduction of the current "on-demand helper system" will promote a better handling of human factors in the procedures of clinical laboratories.