Fifty-one normal subjects, 337 with ocular hypertension, and 55 patients with glaucoma underwent C-30-2 testing on the Humphrey Field Analyzer on at least three occasions over a 6-year period. The time between tests was approximately 1 year. Using the manufacturer's standard for a reliable field (false-positive and false-negative rates, less than 33%; fixation losses, less than 20%), no trends in the proportion of reliable fields or the component indices were observed over time. Four percent of normal subjects, 9% of those with ocular hypertension, and 8% of patients with glaucoma were unable to meet the reliability standard every time they were tested. This repeated lack of reliability was due almost exclusively to fixation losses. However, patients with glaucoma were more likely to have repeatedly high false-negative responses than those with ocular hypertension or normal subjects, providing further evidence that false-negative responses are more indicative of glaucoma than of patient reliability.