Abstract: Experiments were undertaken at the Usmanu Danfodiyo University Fadama Teaching and Research Farm, Sokoto in 2004 and 2005 dry seasons to determine the effect of different nitrogen levels (0, 50, 100 and 150 kg N ha-1) and intra-row spacing (10, 15, 20 and 25 cm) on the growth and yield of onion. Results revealed that nitrogen and intra-row spacing as well as their interaction, significantly affected plant height, number of leaves, crop growth rate, individual bulb weight, bulb diameter and total bulb yield per hectare. Nitrogen at the rate of 100 or 150 kg N ha-1 gave the best results and was statistically at par in all the parameters measured. Tweenty and 25 cm intra-row spacing were found to have recorded the highest and statistically similar values. The optimum yield of onion bulbs (30.83 t ha-1) was obtained from 15 cm intra-row spacing combined with 100 kg N ha-1. However, for large bulb size, application of 150 kg N ha-1 in plants spaced at 25 cm intra-row spacing and 20 cm inter-row spacing may be recommended.