Assessment was made of sex chromosomes and autosomes based on measuring their areas in the Polish landrace, and of the connection of the observed polymorphism with reproductive traits. The average area of sex chromosomes in examined sows was 7.4779 μm2, with the values ranging from 6.9739 μm2 to 8.1331 μm2. And the average autosomes area was 143.7742 μm2. Considerably greater variability was found within the sex chromosomes area than the autosomes area. The variability index of the chromatids area of sex chromosomes was between 0.3182% and 7.9053%. The variability of autosomal chromosomes area, however, was between 1.0491% and 1.3069%. The average areas of sex chromosomes and autosomes as well as the average total areas of chromosomes proved relatively highly and positively correlated with the number of piglets born in the fourth litter, and the values of correlation indexes were respectively r = 0.4044, r = 0.3257 and r = 0.3488.