Reinforced concrete slabs have been known to exhibit considerable strength when tested to failure under an increasing transverse load. This reserve in strength is known to be due to the development of membrane forces whilst the slab is under these transverse loads. The overall effects of the membrane forces depend on the slab edge restraints provided. In this thesis an attempt is made to find a suitable mathematical model to accurately predict the load-deflexion characteristics of the slab using the Finite Element approach. The Finite Element equations are set up for the slab considering the presence of membrane forces, associated with large deflexions, and plasticity also associated with material non- linearity. The simple four noded rectangular plate Finite Element is used in formulating the equations. Slab deflexions are traced from zero load to failure using the Incremental and Step by Step Iterative approach to solve the nonlinear Finite Element equations. The plastic distortions are controlled by checking for equilibrium at each load level with the out of balance forces redistributed to satisfy a square yield criterion. The experimental results from 54 reinforced micro-concrete slabs (made up of 18 square panels and 36 rectangular panels) are presented, and these are compared with the theoretically predicted results. From the comparison of the experimental and the theoretical results the accuracy of the theoretical results is determined and suggestions made for future research on its improvement and development.