Cotton being a long duration, wide spaced and relatively slow growing crop in early stages, is subjected to a severe weed infestation. Weeds have always been a bottleneck for crop production. Inadequate weed control at appropriate stage is considered as a major constraint for high yield. Cotton was very sensitive to weed competition in the first 60 days of crop growth. The period of weed interference, crop damage and the critical period of crop-weed competition were 30 to 60 days which occupied 50 per cent of the whole cotton growing period. Seed cotton yield loss increased with the increase in the duration of competition and maximum loss was observed due to full season competition. Weed infestation in cotton has been reported to offer severe competition and causing yield reduction to an extent of 40 to 85 per cent. Due to their high competitive ability, weeds compete for resources thereby affecting productivity of cotton. Hence, a brief review is presented on the nature of weed spectrum in cotton, competition between crops and weeds, their effect on growth and yield, quality of cotton.