Premature rutting is a common problem with asphalt concrete pavements, particularly when they are subjected to frequent heavy-axle loading. Producers of asphalt modifiers claim that polymers reduce rutting and other distresses by providing stability and durability to the pavement. This project evaluates and compares two modifiers of a dense graded hot-mix asphalt overlay for performance, cost, and ease of construction. A styrene-butadiene (vulcanized) binder has been the standard additive used by the Oklahoma Department of Transportation (ODOT) as an AC modifier. It is a thermoplastic polymer blended with liquid asphalt at the refinery before shipping. ODOT is now testing ULTRAPAVE 70, a new product from Goodyear. This liquid styrene butadiene rubber latex thermoset polymer is shipped directly to the asphalt plant in a tanker and fed into the pugmill or in-line to the drum mixer. A maintenance overlay contract was awarded for I-40 in Division V, Bekham County and an 8.85 km (5.50 mi) section of the outside eastbound lane was selected as teht est site. A 4.15 km (2.58 mi) section was overlaid with the standard thermoplastic polymer mix and a 4.70 km (2.92 mi) section with the ULTRAPACE 70 mix. A comparative analysis of the performance of the two mixes found them to be equally effective in reducing rutting. The ULTRAPAVE 70 was, however, a more versatile product which allowed for simpler alternation between modified and unmodified mixes at the batch plant. It is recommended that the use of ULTRAPAVE 70 be permitted on ODOT projects.