Three experiments were conducted in Maricopa, Marana, and Glendale, Arizona in 2001 to measure cotton growth, yield, micronaire, and production costs in single and double seed line per bed systems on 32 and 40 inch beds. Canopy development was faster and canopy closure was greater in the double seed line than in the single seed line systems and was greater in the 32 inch than in the 40 inch row systems. At Maricopa, the single line 32 inch system yield of 1571 lbs./A was significantly greater than the yields of the other seed line/row spacing systems. The yields of the single line 40 and the double line 32 inch systems were not significantly different at 1476 and 1411 lbs. of lint/A, respectively, and the yields of the double line 32 and the double line 40 inch systems also were not significantly different at 1411 and 1396 lbs. of lint/A, respectively. There were no significant lint yield differences at the Marana or Glendale location. At Marana, the lint yields were 1063 and 1066 lbs./A for the single and double seed line 40 inch row spacing systems, respectively. At Glendale, the single and double seed line 38 inch row spacing systems yielded 1474 and 1551 lbs. of lint/A, respectively. In all 2001 experiments, there was a trend for reduced micronaire in the double seed line per bed systems compared to the single seed line per bed systems. At Maricopa, the average micronaire was 5.0 and 4.7 for the single and double seed line per bed 32 inch row system, respectively, and 5.2 and 4.9 for the single and double seed line per bed 40 inch row systems, respectively. At Marana, the micronaire was 4.7 and 4.5 for the single and double seed line per bed 40 inch row systems, respectively. At Glendale, the micronaire was 5.1 and 4.6 for the single and double seed line per bed 38 inch row systems, respectively. Production costs were similar for the single and double seed line per bed systems. Additional research will be conducted in 2002 to determine the optimum plant populations and in-row plant spacings for double seed line per bed production systems.