Field experiments were conducted for two successive cropping seasons from 2008/09 to 2009/10 at Kenilworth experimental station to evaluate the response of maize to variable row spacing and plant densities. The treatments used were three row spacing (0.225, 0.45 and 0.90 m) and five plant densities (5, 7.5, 10, 12.5 and 15 plants m-2) combined in a factorial arrangement and laid out in a randomized complete block design with three replications. The results revealed that row spacing and plant density influenced yield and yield components. Number of seeds per row, kernels per ear and ear length were significantly higher at a row spacing of 0.90 m with a plant density of 5 plants m-2. The highest biomass was observed at row spacing of 0.225 m with plant density 10 plants m-2 while grain yield, harvest index and grain yield water use efficiency were significantly highest a at row spacing of 0.45 m with a plant density of 10 plants m-2. Based on this finding, row spacing 0.45 or 0.90 m with plant density 10 plants m-2 could be adopted for ultra-fast maize hybrid production under irrigation in semi-arid environment.