Field experiments were conducted in North Carolina, Georgia, and Texas to determine if grass control is affected when postemergence-applied graminicides are mixed with 2,4-DB. Grass species evaluated included broadleaf signalgrass [Brachiaria platyphylla (Griseb.) Nash], goosegrass [Eleusine indica (L.) Gaertn.], johnsongrass [Sorghum halepense (L.) Pers.], large crabgrass [Digitaria sanguinalis (L.) Scop.], southern crabgrass [Digitaria ciliaris (Retz.) Koel.], and Texas panicum (Panicum texanum Buckl.). Mixing 2,4-DB with the graminicides reduced grass control 8 to 15% at five of 11 locations. The antagonism was not specific for a particular grass species or graminicide, and it was not restricted to grasses under adverse growing conditions. Applying the 2,4-DB 24 hours after graminicide application alleviated the antagonism. Applying the 2,4-DB 24 hours before the graminicides overcame the antagonism at three of the five locations.