Twenty-nine s-triazines were evaluated as subsurface and surface preemergence sprays for the control of crabgrass in corn, grain sorghum, soybean, and cotton and as directed postemergence sprays in cotton. In preemergence experiments corn was tolerant to most chloro-alkylamino-s-triazines but was severely injured by most methoxy- and methylmercapto-alkylamino-s-triazines. 2-Chloro-4,6-bis(isopropylamino)-s-triazine [propazine], 2,4-bis(ethylamino)-6-trichloromethyl-5-triazine, and 2-chloro-4-isopropylamino-6-methylamino-s-triazine were about equally effective for selective preemeregnce weed control in grain sorghum. 2,4-Bis(ethylamino)-6-trichloromethyl-s-triazine and perhaps 2-methoxy-4,6-bis [(3-methoxy)propylamino]-s-triazine were sufficiently active and selective to suggest additional evaluation as preemergence herbicides for soybeans. Cotton exhibited tolerance to certain methylmercapto derivatives; 2,4-bis(isopropylamino)-6-methylmercapto-s-triazine [prometryne] as a preemergence and as a directed postemergence spray appeared especially promising for control of weeds in cotton. Generally methoxy- and methyl-mercapto-alkylamino-s-triazines as preemergence and postemergence sprays were more effective for controlling crabgrass than corresponding chloro-alkylamino-s-triazines. The initial and residual toxicities of 14 of the more promising s-triazines were compared in four soils of the southern United States. Initial effective levels of the methoxy and methylmercapto derivatives varied more among soils than those of corresponding chloro derivatives. In most cases methoxy s-triazines were more toxic to the fifth oat crop than corresponding chloro s-triazines whereas chloro s-triazines exhibited the greatest initial toxicities. Certain methylmercapto derivatives appeared fairly persistent also.