This master thesis purports to address the effects of different filler types in asphalt mastics and relate the differences to asphalt mixture properties and volumetric composition. Due to variations in properties for different filler types, e.g. particle size, density, mineral composition, Rigden voids, specific surface area and binder interaction, the same filler amount by weight yields variations in occupied volume and bind different amounts of bitumen. Uncontrolled variations of the filler fraction can cause binder drainage as a result of insufficient reinforcement or a dry mixture with unsatisfactory coating of the aggregates. The literature review focused on outlining characteristics and effects of different fillers and mastic composition and to relate variations in mixture performance to filler types and the ratio of filler to binder. An experimental laboratory research has been conducted to evaluate the effects of using different filler types. Mixtures with limestone and hydrated lime have been compared to mixtures with natural sieved dust from Vassfjell and Steinkjer aggregates on the 0.063 mm sieve. The results showed that the Rigden void content in the filler has an effect on the compacted asphalt mixture. Higher Rigden void content yields higher indirect tensile strength and a tendency to lower the abrasion resistance. The outcome from cyclic compression test was scattered, and there were too few data point to give any adequate conclusion. The tests showed that the F/A-ratio by mass or volume had less influence on the mixture performance. The air void content and the degree of compaction of the specimen greatly influenced the outcome, which coincide with results in the literature. The air void content was related to the Rigden void content, and in the literature it was found that higher Rigden void content in the filler gave higher air void content in the compacted specimens. Furthermore, increasing Rigden void content tended to increase the effective volumetric filler particle concentration in the mastics.