Grain of three varieties of hybrid sweet corn was harvested and analyzed at approximately 15, 30, 45 and 60 days after pollination to establish variation in composition and amino acid content among varieties and during course of grain maturation. In all three varieties, percent protein content on a dry basis dropped markedly after 15 days post‐pollination but remained fairly constant at 12–13% during later development. Fat increased steadily from 3 to 7 or 8% (dry basis) in all varieties. Lysine content decreased after 15 days, but sulfur amino acids increased to a maximum at 60 days. At 28–30 days, when sweet corn is generally harvested for canning, lysine content of the grain ranged from 3.8–4.3g per 100g of protein.