One hundred tomato cultivars were direct seeded, and treated with one postemergent application of Lcxone at 28 days following the first irrigation. Applications of 0.56, 1.12, 1.68 and 2.24 kg ai/ha (0.50, 1.00, 1.50 and 2.00 lbs ai/ac) of metribuzin was made directly over the plants. Ten days after the application, the observed results were as follows: six cultivars were tolerant to all treatments, while 33 were tolerant up to the 1.68 kg/ha level only. Sixty of the cultivars demonstrated tolerance up to the 1.12 kg/ha level. One cultivar was susceptible to all rates tested. Seven weed species were encountered, and their response to the postemergent herbicide was: complete kill of Digitaria sanguinalis, Trianthema portulacastrum, Amaranthus dubids, Phyllanthus niruri, Kailstromea maxima and Portulaca oleracea at all rates. Echinochloa colonum was tolerant at 0.56 and 1.12 kg ai/ha level; and susceptible at the 1.68 and 2.24 kg ai/ha rates.