  BRST quantization is carried out for a model of p-branes with second class
constraints. After extension of the phase space the constraint algebra
coincides with the one of null string when p=1. It is shown that in this case
one can or can not obtain critical dimension for the null string, depending on
the choice of the operator ordering and corresponding vacuum states. When p>1,
operator orderings leading to critical dimension in the p=1 case are not
allowed. Admissable orderings give no restrictions on the dimension of the
embedding space-time. Finally, a generalization to supersymmetric null branes
is proposed.
