A research trial was conducted with laying hens from 143 to 311 days of age to study the influence of supplementary vitamin C (ascorbic acid) on various production parameters. Vitamin C at 0, 50, 100, 200, and 400 ppm was each fed to groups of 80 birds that were subdivided into 16 replicates of 5 birds each. The trial was initiated at onset of production when experimental diets were provided, and continued for six periods of 28 days each. The study was started during April and continued into September to subject birds to high environmental summer temperatures. Egg production, feed consumption, feed per dozen eggs, egg weights, egg specific gravity, and interior egg quality (Haugh units) were measured for each 28-day period. Egg production and egg weights were not significantly affected by dietary treatments except for the fifth 28-day period when egg production was slightly higher for the control group than for the vitamin C groups. Feed consumption was generally higher for the control group, and feed conversions were generally better for the groups supplemented with 50 and 100 ppm vitamin C. Egg specific gravity was significantly affected by diet in four of the six periods with eggs from the highest vitamin C treatments (200 and 400 ppm) generally having higher specific gravity values.