In this study, we investigated fly ash replacement of the fine aggregate in hot-mix asphalt concrete mixtures. Fly ash was obtained from the Soma thermal power plant. Fly ash in amounts of 5, 6, 7, and 8% by total aggregate weight was added as an additive to asphalt concrete mixtures. Mixtures were prepared without additives containing filler, which had the same percentages as the fly ash mixtures, and briquette samples were prepared from mixtures with fly ash and with filler. Marshall tests were applied to the samples, and optimum asphalt contents were determined. In the optimum conditions, parameters were determined, which were stability, practical specific gravity, void, flow, and max theoretical specific gravity. The results indicate that the stability values obtained from mixtures with fly ash are higher than mixtures from filler. The highest stability value was obtained from 5% fly ash added mixture, which was 1,630 kg in optimal conditions.