The effect of 30 inch row spacing versus 40 inch row spacing on irrigated cotton yield and quality was evaluated for six years in the Rio Grande Valley of South Texas beginning in small experimental plots and proceeding to larger field tests in the later years. In each of the six years the lint weight per acre from 30 inch row spacing was significantly greater than from the 40 inch row spacing. The difference between 30 inch and 40 inch ranged from a low of 65 pounds per acre in 1984 to a high of 198 pounds per acre in 1986. The 1989 lint weight difference between the two row spacings was 157 pounds per acre. The differences between treatments within years were significant at the five percent level using the student "it" test for all six years. Over the six years, the average lint increase was 120 pounds per acre and the average selling price was $.5875 per pound for the cotton. The mean price coupled with the average increase in yields from 30 inch culture versus 40 inch culture provided an increased gross return of approximately $70.00 per acre. Adjustments were made to South Texas Crop Budgets to estimate the expected net return from each row spacing for each year tested. The average net return was approximately $31.00 per acre increase due to switching from the 40 inch row to the 30 inch row spacing.