Field experiments were conducted during winter seasons of the year 2002-03 and 2003-04 to study the effect of increasing densities of common lambsquarters (Chenopodium album L.) and wild onion (Asphodelus tenuifolius Cav.) on the productivity of winter onion. There was significant decrease in onion bulb yield even with density of C. album at 5 plants/m2 compared to weed free treatment. The per cent yield reduction ranged from 16 to 40% at densities of C. album from 5 to 160 plants/m2 over weed free treatment, respectively. Similarly, 80 plants/ m2 of A. tenuifolius and more caused significant reduction in onion bulb yield as compared to weed free treatment. The onion bulb yield reduced from 2.6 to 52.6% by increasing the density of A. tenuifolius from 20 to 640 plants/m2, respectively over weed free treatment