Immunoreactive insulin (IRI) concentration in sows colostrum has been previously proven to be much higher than that in blood. The experiment was carried out to show the influence of endogenous and added insulin in sows colostrum on insulinaemia and glycaemia of newborn piglets. In colostrum collected from 3 control and 5 experimental sows before loading, basal insulin concentration were 1.595 and 1.365 nM-1, respectively, and calculated for all 8 sows together were 1.451 nM-1 (SEM +/- 0.289). Basal plasma insulin concentrations calculated for 68 healthy piglets before sucking were little differentiated (mean 0.318 +/- 0.044 nM l-1), whereas glucose initial concentrations for those piglets (mean 3.581 +/- 0.275 nM l-1) were highly differentiated. Intramuscular loading of 5 experimental sows with insulin (80 I.U. per animal) caused an increase in the concentration of insulin in colostrum from 1.365 to 3.449 nM l-1 (0.01, P less than 0.02). The mean insulin level (0.313 +/- 0.04 nM l-1) in experimental piglets blood plasma (n = 42) increased significantly to 1.234 +/- 0.07 (P less than 0.001) after suckling by sows loaded with exogenous insulin. Glycaemic response of those two piglets litters was poor but showed a statistically significant increase (P less than 0.001). The glucose concentrations in blood plasma samples of the other three litters did not changes after sucking. The experiment excluded the hypothesis that high level of insulin in colostrum could be the cause of hypoglycaemia in healthy piglets after sucking.