Milk lipid and fatty acids were measured from women with insulin-dependent diabetes mellitus (IDDM), a comparison group of women without diabetes, and reference women. Milk samples were collected 80 min after breakfast at 2, 3, 7, 14, 42, and 84 d postpartum (pp). Total lipid and medium-chain fatty acids (MCFAs) in the group with IDDM were similar to or greater than those of control and reference groups at all times and were within normal, reported ranges. Milk long-chain polyunsaturated fatty acids (LC-PUFAs) were lower in women with IDDM from 14 to 84 d pp. Lower milk LC-PUFAs may be a result of altered fatty acid metabolism in women with IDDM.