As a quality control service for the CSII (continuous subcutaneous insulin infusion) outpatient clinic a technical monitoring of insulin delivery devices was established. Technical check-up was performed routinally before and optionally under patient application if there was unexplained variation in apparent insulin effects. Quality control of n = 84 pumps of various types gave the following results: screening of dosage precision parameters revealed remarkable hour-to-hour variance and deviation range even for brand new devices. In contrast systematical long time deviation from nominal pump value was low. Used infusion pumps did not differ significantly from new pumps, but there was a slight trend to diminished delivery. N = 17 pumps were checked because a malfunction was suspected. In 9 of these devices technical failure was verified which in 4 cases was associated with hyperglycemia. From these experiences, we conclude technical monitoring a necessary option when running a CSII outpatient clinic.