Resilient modulus is an important property for asphalt concrete design and for mechanistic analysis of pavement response under traffic loading. This study investigates the different factors affecting the resilient modulus of hot mix asphalt. A fractional factorial design of experiment was carried out to investigate six factors each factor was studied at two levels. These factors are: the maximum nominal aggregate size, specimen diameter and thickness, the load pulse form and duration, and the compaction method. Two types of hot mix asphalts with different maximum aggregate sizes (10 mm and 14 mm) were studied. Gyratory and Marshall compaction methods were used to prepare the specimens. Sinusoidal and triangular load pulse forms were used in the measurement of the resilient modulus. This study attempts to examine how the different factors interrelate to affect the resilient modulus. In addition to this, two other investigations will be carried out. The first is the comparison of the strain backcalculated using the resilient modulus test results with the strain measured using strain gages and strain values obtained from finite element modelling (FEM), and determine whether the FEM or the closed form equation is the more accurate method for determining strain. The second is the investigation of the relationship between the flexural, complex and resilient modulus. Analysis of the factorial experimental design showed that the maximum nominal aggregate size is the most important factor affecting the resilient modulus, followed by the load duration, the specimen geometry represented by the thickness and diameter then the interactions between the different factors. The strain comparison suggested that the closed form equations were indeed a suitable approach to determine maximum horizontal strain during a resilient modulus test. The modulus comparison suggested that it is possible to predict either resilient, complex and flexural modulus given that only one of them is known, but only for AC10 specimens.