The concentration of total protein and albumin was examined in the blood plasma of pig foetuses on the 112th day of pregnancy, piglets early weaned from sows and after 14 days, pigs at slaughter weight, and two groups of porkers given different amounts of protein from weaning to the age of 122 days. A relationship was demonstrated between the level of plasma albumin on the one hand and body weight and feed protein content on the other. As distinct from this, the differences in the levels of total protein were not statistically significant in porkers and pigs with different weight. In piglets weaned from sows, the concentration of total protein showed a marked decrease but plasma albumin content did not drop, although feed intake and body weight gains were low. Attention is drawn to some physiological peculiarities of both parameters in pig development and emphasis is made on the diagnostic value of plasma albumin. The correction factor derived from different capacity of the swine of human serum albumin, serving as standard, was used for the determination of plasma albumin by the inversion colorimetric method based on the ability of binding bromocresol green in buffered solution.