  The masses of $uudd\bar s $ and $uudd\bar d$ pentaquarks are evaluated in a
framework of the Effective Hamiltonian approach to QCD using the Jaffe-Wilczek
$[ud]^2\bar q$ approximation. The mass of the $[ud]^2\bar s$ state is found to
be $\sim 300-500$ MeV higher than the observed $\Theta^+(1540)$ mass.
