The guinea pigs were administrated vit. A (400 i.u.), vit. B₂ (1 mg) or vit. B₁₅ (5 mg). On the 9-th day of the experiment part of them was infectpd with 5000 invasive eggs of Ascaris suum. The invasion lasted 6 days and was controlled by lungs and kidney weight, and number of larvae in the lungs. The activity of amylase was determined by saccharogenic method in both organs. In the lungs of infected animals the activity of alpha-amylase was abouth 3 times lower than in the control. The infection of guinea pigs which were given vitamins did not cause change of enzyme's activity. In the kidney directive tendency was the same, but the differences were smaller. The infection resulted in an increase of relative mass of lungs. This index and number of larvae was considerable smaller in guinea pigs with vitamins A and B₁₅ administration. Any testing agent did not cause change of relative weight of kidney.