This experiment examined the accuracy of capillary blood glucose monitoring using the visual glucose oxidase strip (Chemstrip) procedure. Also, the effects of a certification program for nurses on the accuracy of glucose oxidase strip monitoring by registered nurses were analyzed. Seventy nurses and 123 patients participated. Data were collected from nurses' recordings of visual Chemstrip procedure results and from the concurrent laboratory blood glucose determinations for 3 months. The data included 70 Chemstrip recordings and 70 concurrent laboratory blood glucose recordings in the experimental group and 68 Chemstrip and 68 concurrent laboratory glucose recordings in the control group. Data analysis revealed that the accuracy of the nurses' performance of the glucose oxidase strip procedure was inadequate. A certification program did, however, dramatically improve the accuracy of the procedure. Proximity of time between the certification program and the performance of the glucose oxidase strip procedure did not affect accuracy.