Reflectance meters containing memory chips were used in a study that addressed several questions concerning routine use of self-monitoring of blood glucose (SMBG), including accuracy of patient blood glucose (BG) diaries, reliability of self-reported frequency of SMBG, and adherence to recommended SMBG regimen. Thirty adults with insulin-dependent diabetes used memory meters and recorded test results in diaries for 2 wk while performing their normal SMBG regimen. Analysis of glucose diaries showed that only 23% of the subjects had no diary errors and 47% had clinically accurate diaries (less than 10% error rate). The most common types of errors were omissions of values contained in meter memory and additions of values not contained in meter memory, with significantly more omissions than additions. Alterations of test values (e.g., changing a 300-mg/dl reading to 200 mg/dl) were extremely rare. There was no difference in the rate of errors that resulted in a more positive clinical profile (omitting unacceptable values and adding acceptable values) or a more negative clinical profile (omitting acceptable values and adding unacceptable values). Examination of the actual frequency of SMBG showed that most subjects (56.6%) measured their BG an average of two to three times each day. Self-report of SMBG frequency correlated with both actual frequency and HbA1. Although actual frequency of SMBG was not related to physicians' recommendations, the majority (64%) of subjects were self-testing as often or more often than they had been instructed.