Seventy-seven diabetics with a duration of the disease ranging from 2 to 55 years (average 18.5 years) were studied with infrared videopupillometry. The prevalence of diabetic autonomic neuropathy at the pupillary control system (pANP) was studied comparatively using several pupillary tests. The average prevalence using age-dependent parameters was 30.2% [maximal pupillary area: 22.1%, maximal contraction velocity: 24.7%, contraction velocity at 1 s (CV1): 28.6%, and dilation velocity at 6 s (DV6): 45.5%]. Comparing these percentages to prevalences of other diabetic late complications, e.g. retinopathy (49.4%), DV6 seems to be good for the diagnosis of pANP. If CV1 and DV6 are expressed in percent of the maximal pupillary area (CV1% and DV6%), they become age-independent. The average CV1% and DV6% of diabetics differ highly significantly from those of normals (CV1%: 58.6 +/- 14.5 vs. 64.1 +/- 6.4%, 2 p less than 0.005, and DV6%: 6.0 +/- 2.9 vs. 7.3 +/- 1.1%, 2 p less than 0.001). The average prevalence of pANP using these age-independent parameters was 25.4%. These data suggest that the prevalence of pANP, especially disorders of pupillary dilation (DV6), is high in long-standing diabetes. Furthermore, CV1% and DV6% have proved to be valid parameters in finding differences in the light reflex in non-age-matched study groups.