The action of a new semi-synthetic insulin preparation (30% soluble, 70% NPH insulin from Organon Laboratories Eragny sur Epte France) was studied in 6 healthy male volunteers using the euglycemic clamp technique (Biostator GCIIS) and compared with another 30/70 NPH (Actraphane Novo). Insulin levels, inhibition of C peptide secretion and glucose consumption were determined. There was a time lag between the maximum glucose need (167 +/- 18 mg/Kg/15 min at the 195th minute after the injection) and the peak plasma insulin level (98.3 +/- 8.5 uu/ml at the 105th minute following the injection). The maximum glucose need was followed by a slow fall in insulin levels with a duration of action of 17 hours. The total glucose need was the same as for Actraphane, although Actraphane had a slower action with a lower peak glucose need (144 +/- 18 mg/Kg/15 min at the 280th minute after injection). The two preparations had the same duration of action.