Sows and gilts of the Great White Polish (GWP) breed were classified into groups of 10 each: gilts 8 mo of age (A), sows over 1 yr old with an average litter size of five (BI) and eleven (BII), 2- to 3-yr-old sows with an average litter size of five (CI) and nine (CII), 4- to 6-yr-old sows with an average litter size of six (DI) and nine (DII). Gilts of group A were necropsied on d 10 of the estrous cycle while sows were necropsied 120 to 360 d postpartum. A blood sample obtained by vena cava puncture immediately before exsanguination was quantitated for total cholesterol, free cholesterol, cholesterol ester, total lipid, triglyceride, high and low density lipoprotein and chylomicrons. Postmortem angiograms of the uterine vasculature were evaluated for occurrence of arteriosclerotic lesions of the arteries and their branches. Sections of blood vessels from areas of restriction were examined histologically and quantitated for lipids and proteolytic and lipolytic enzyme activities. With the exception of high density lipoproteins and chylomicrons, serum concentrations of various lipids increased (P less than .01) with age. Restrictions of the lumen were found in uterine arteries and their branches of most gilts in group A and in sows in groups B, C and D, irrespective of litter size. Histology of uterine artery revealed preatherosclerotic lesions in groups B through D. No relationship between the incidence and degree of sclerotic lesions and litter size was evident. However, the incidence and degree of sclerotic lesions increased with age and parity. Results from histopathology were supported by results from measurement of lipids and enzyme activities of the uterine artery wall. Conception rates of sows in groups C and D were lower than those of group B. Many of these sows (70%) failed to conceive during 1 yr even though they displayed normal estrous cycles.