  We study a bosonic ladder with two coupled chains using the finite size
density matrix renormalisation group method. We show that in a commensurate
bosonic ladder the critical on-site interaction ($U_C$) for the superfluid to
Mott insulator transition becomes larger as the inter-chain hopping
($t_\bot$)increases. We analyze this quantum phase transition and obtain the
phase diagram in the $t_\bot -U$ plane.
