Title : Effect of electron correlation on positronium formation in positron-helium scattering. authors :Puspitapallab Chaudhuri$^1$, S. K. Adhikari$^1$, B. Talukdar $^2$ and S. Bhattacharya $^2$. Affiliation : $^1$Instituto de F\'isica Te\'orica, UNESP, 01405-900, s\~ao Paulo, S\~ao Paulo, Brazil $^2$ Department of physics, Visva Bharati University, Santiniketan 731235, India Summary : A three-parameter correlated wave function for the helium ground state is used to study the positronium formation from helium. An exact analytical expression for the first Born scattering amplitude for Ps-formation and differential and total cross sections are calculated. It is demonstrated that the inner electronic correlation of the target atom plays a crucial role in explaining the discrepency between theory and experiment.