In 1972, a 50-yr study of seed longevity was initiated at Stoneville, Mississippi. Weed seeds were collected from 20 locallygrown species and mixed with soil. Replicate samples were placed in polypropylene screen envelopes and buried at soil depths of 8, 23, and 38 cm. Seed germination and viability were determined by germination tests and 2,3,5-triphenyl-tetrazolium chloride (TTC) treatments with recovered seeds. In general, the depth of burial had little effect on seed longevity. Based on the averages of the means at the three depths, the percentages of seeds still viable after burial for 2.5 yr were: spurred anoda [Anoda cristata (L.) Schlecht.] 71%; purple moonflower (Ipomoea turbinata Lagasca y Segura) 71%; johnsongrass [Sorghum halepense (L.) Pers.] 62%; velvetleaf (Abutilon theophrasti Medic.) 58%; goosegrass [Eleusine indica (L.) Gaertn.] 33%; hemp sesbania [Sesbania exaltata (Raf.) Cory] 29%; Texas panicum (Panicum taxanum Buckl.) 24%; common cocklebur (Xanthium pensylvanicum Wallr.) 18%; common eveningprimrose (Oenothera biennis L.) 14%; large crabgrass [Digitaria sanguinalis (L.) Scop.] 12%; sicklepod (Cassia obtusifolia L.) 10%; common purslane (Portulaca oleracea L.) 10%; white morningglory (Ipomoea lacunosa L.) 8%; redroot pigweed (Amaranthus retroflexus L.) 7%; prostrate spurge (Euphorbia supina Raf.) 6%; prickly sida (Sida spinosa L.) 5%; redvine (Brunnichia cirrhosa Gaertn.) 3%; Florida beggarweed [Desmodium tortuosum (Sw.) DC.] 3%; barnyardgrass [Echinochloa crus-galli (L.) Beauv.] 1%; and chickweed [Stellaria media (L.) Cyrillo] 0%.