The effects of petroleum mulches on plant response to herbicides were studied at the Farmington Field Station . The herbicides were applied to the soil preemergent and by incorporation at one-half, normal and double the recommended rates with asphalt overlay. The herbicides and crops used were : Atrazine and Ramrod on sweet corn, PEBC and Diphenamid on tomatoes and EPTC and Trifluralin on snap beans. Germination, overall crop rating, grass and broad leafed weed control and yields were measured. Data recorded from these trials showed that herbicides are as effective under the asphalt when compared to plots with herbicide but no asphalt. Considering all herbicides and conditions, overall crop growth and weed control were not increased or decreased by the asphalt mulch. Germination and yield were not affected by the interaction of herbicides with the asphalt overlay on the three crops.