This thesis investigates the behaviour of timber-concrete composite beams with mechanical shear connectors. The analysis of these structures is complex due to the discontinuity caused by slip at the interface between the timber and concrete and can only be achieved by the use of sophisticated analytical techniques. A literature review has been carried out highlighting the fact that only a limited amount of theoretical and experimental work exists on timber- concrete composite beams. The fundamental objectives of this study were to develop suitable analytical and experimental models so as to better understand the behaviour of these structures. Fifty seven push-out specimens and seven beams were tested in order to determine the load/slip characteristics of the coach screw connectors and how these influence the behaviour of the beams. It was found that the bond and friction at the timber-concrete interface had a significant effect on the behaviour of the joints and beams. Analyses were carried out using a fully non-linear finite element package, LUSAS. The finite element model developed consisted of standard two dimensional elements and the results from the beam tests were used in a validation exercise. In general, good agreement was obtained for the stiffness of the beams throughout their loading history. Studies were carried out using the analytical model to determine the influence of the main parameters on the stiffness of the beams. The connector stiffness and timber properties were found to have a strong influence while the concrete properties were not significant at working load level. Further analytical studies were carried out for a wide range of geometric properties. The information obtained was used in the formulation of a design procedure which allowed for slip at the interface of the beams. Recommendations are included for future research on timber-concrete composite beams.