We examined whether fear of hypoglycemia in insulin-dependent diabetes mellitus was associated with (a) higher levels of trait anxiety and general fearfulness, (b) difficulty in differentiating symptoms of anxiety and hypoglycemia, and (c) past experience with hypoglycemia. Joslin Diabetes Center outpatients with Type I and Type II diabetes (N = 232), all requiring insulin, were surveyed. Type I patients experienced significantly more fear of hypoglycemia than Type II patients. For the Type I and Type II groups, higher scores on the Worry subscale of the Hypoglycemia Fear Survey (HFS-W) were associated with higher levels of trait anxiety and fear. Higher scores on the Behavior subscale (HFS-B) were associated with higher levels of fear. Among Type I subjects only, HFS-W scores were also positively associated with past hypoglycemic experience and with difficulty in differentiating anxiety and hypoglycemic symptoms. These latter relations remained significant even after the variance resulting from trait anxiety and fear was removed. Other significant associations with HFS-B scores were not observed.