This paper reports on experimental investigations on the influence of maximum size of coarse aggregate, cement and coarse aggregate contents on the elastic and mechanical properties of high strength concreet (HSC). It has been observed that the compressive strength increases as the maximum size of coarse aggregate increases at higher coarse aggregate contents, while it decreases at lower coarse aggregate contents. The modulus of elasticity increases as the maximum size of aggregate and the coarse aggregate content increase. The strength and stiffness of the high strength concrete increases as the cement content increases. However, at cement contents between 425 and 450 kg/m 3, the strength and stiffness of concrete seem to be higher with 16 mm coarse aggregate. The maximum size of coarse aggregate ranges between 10-16 mm for producing high strength concrete. The Poisson's ratio has been observed to be insensitive to the mix proportions of concrete whose mean value is about 0.19. Empirical equations have been proposed to evaluate the tensile strength and modulus of elasticity as functions of the compressive strength. The proposed equation estimates higher values of modulus of elasticity than those expressions proposed by ACI code and ACI Committee 363, while IS 456 estimates slightly higher values. The tensile strength estimated by IS 456 is much higher for HSC, while the proposed equation lies in between those specified by the ACI 318 and ACI Committee 363.