Accuracy of self-monitoring of blood glucose (SMBG) using Chemstrip bG (Bio-Dynamics, Indianapolis, Indiana) was studied in 90 randomly selected children with insulin-dependent diabetes mellitus (IDDM). For 28 children (mean age 8.3 ± 3.6 yr) a parent routinely read the Chemstrip at home. The remaining 62 children (mean age 13.7 ± 2.8 yr) read the Chemstrip themselves. Each child or parent analyzed 20 capillary blood samples using Chemstrips and answered a questionnaire on SMBG. The accuracy of SMBG of the group was high (mean correlation coefficient = 0.89 ± 0.05), but consistency of measurement was variable (mean standard deviation = 1.90 ± 0.57) and there was a general tendency to underread Chemstrips (mean y-intercept = 1.05 ± 1.48; mean slope = 0.80 ± 0.17). For each subject, 0–65% (mean of 34%) of readings were within 10% of the laboratory measurement, and 17–100% (mean 68%) within 20%. These results indicate that most subjects were fairly accurate in reading Chemstrips; however, analysis of accuracy is useful in identifying individuals who are inaccurate or inconsistent in SMBG. Continuing supervision of SMBG is necessary in children with IDDM.