Pesticide regulations based on pesticide mobility data derived from row crop systems may not appropriate for bermudagrass systems because organic matter binds pesticides and bermudagrass systems can have a thatch layer at the soil surface which is rich with organic matter. ¹⁴C-labeled simazine was applied to dormant bermudagrass (Cynodon dactylon) and fallow soil in lysimeters stored in a cold growth chamber (5 ^oC) and to actively-growing bermudagrass and fallow soil in lysimeters kept in a greenhouse (25 ^oC). Following each clipping collection, lysimeters were irrigated with five cm of water every three to four days, and leachate was collected four hours later. After 25 days, lysimeters were divided into the following depth increments: 0-2, 2-4, 4-6, 6-8, 8-10, 10-15, 15-20, 20-25, 25-30 cm. Due to evapotranspiration, actively-growing bermudagrass and warm fallow soil lysimeters yielded significantly less leachate than dormant bermudagrass and cold fallow soil lysimeters indicating less moisture is available for downward movement during summer. The amount of simazine translocated in actively-growing bermudagrass clippings increased from 14,377 disintegrations per minute (DPM) to a maximum of 62,003 DPM and then decreased to 21,314 DPM over a 21 day period. After the addition of 31 cm of irrigation, the greatest quantities of simazine were detected in the 0-2 cm increment of all treatments, and quantities decreased with depth. Although the greatest quantities of simazine in leachate occured in dormant bermudagrass, the reached factor (R_f) calculated for simazine distribution in the soil profile was greatest for cold fallow soil (0.20), followed by dormant bermudagrass (0.17), followed by warm fallow soil (0.16) followed by actively-growing bermudagrass (0.14). Therefore, simazine is least mobile in bermudagrass during periods of high evapotranspiration rates as in summer.