We have studied 27 insulin-dependent diabetic patients since diagnosis for a period of six months; at diabetes onset and later on, ICA were found in 17 of them, whereas they were undetectable in 10 patients: age was remarkably homogeneous in the two groups. At diabetes onset, no significant differences were found in insulin requirement between ICA positive and ICA negative patients; however, six months after diagnosis, we observed that insulin requirement to keep metabolic control was significantly higher in ICA positive than in ICA negative subjects (0.515 +/- 0.2 U/Kg versus 0.22 +/- 0.15 U/Kg, p less than 0.001). Only one remission has been detected in ICA positive group (insulin requirement less than 0.25 U/Kg), while four ICA negative patients had complete remission and three had partial remission. ICA positive patients showed fasting C-peptide values higher than ICA negative (0.5 +/- 0.28 ng/ml versus 1.4 +/- 0.5 ng/m.; p less than 0.001, at rest; 1.1 +/- 0.6 ng/ml; versus 2.6 +/- 1.0 ng/ml, 6 minutes after stimulus; p less than 0.05). Our study suggests that presence and persistence of ICA may be considered an early and predictive marker for a worse beta cell function restoration resulting in a higher insulin requirement.