  An elementary method of determination of the character of the hot phase
transition in 4d four-fermion NJL-type models is applied to non-supersymmetric
and supersymmetric versions of simple NJL model. We find that in the non-susy
case the transition is usually of the second order. It is weakly first order
only in the region of parameters which correspond to fermion masses comparable
to the cut-off. In the supersymmetric case both kinds of phase transitions are
possible. For sufficiently strong coupling and sufficiently large susy-breaking
scale the transition is always of the first order.
