An experiment was conducted at the University of Arizona Maricopa Agricultural Center, Maricopa, Arizona in 1999 to compare and evaluate agronomic and economic differences between Ultra Narrow Row (UNR) and conventional cotton row spacing systems with respect to yield, fiber quality, earliness potential, plant growth and development, and production costs. Row spacing was 10 and 40 inches for the UNR and conventional systems, respectively. Two varieties were evaluated within each row spacing, Sure Grow 747 (SG 747) and Delta Pine 429RR (DP 429RR). Lygus populations were extremely high in the Maricopa, Arizona region in 1999 which resulted in poor fruit retention from early through mid-season. As a result of poor boll load through mid-season, the UNR plots were irrigated and grown later into the season than desired along with the conventional cotton in order to set and develop a later season boll load. The mean lint yield averaged across row spacing was significantly greater (P=0.05) in the UNR row spacing at 1334 lb/A than for the conventional row spacing at 1213 lb/A. SG 747 produced 1426 and 1337lb/A of lint in the UNR and conventional systems, respectively. DP 429RR produced 1242 and 1089 lb/A of lint in the UNR and conventional systems respectively. Fiber grades were all 21 or 31 in both UNR and conventional systems. Micronaire was 4.9 or less in both varieties within the UNR system. Micronaire was high at 5.3 in the conventionally produced SG 747 resulting in discount but was acceptable at 4.7 in the conventionally produced DP 429RR. Length and strength measurements met base standards in all cotton variety and row spacing combinations. Neither the conventional or the UNR cotton production systems were profitable due primarily to high chemical insect control costs and early season boll loss. However, UNR production costs were lower by $0.09 per pound than in the conventional system on a cash cost basis and $0.14 per pound lower when considering total costs including variable and ownership costs.