  We consider a self-consistent system of Bianchi type-I (BI) gravitational
field and a binary mixture of perfect fluid and dark energy given by a
cosmological constant. The perfect fluid is chosen to be the one obeying either
the usual equation of state, i.e., $p = \zeta \ve$, with $\zeta \in [0, 1]$ or
a van der Waals equation of state. Role of the $\Lambda$ term in the evolution
of the BI Universe has been studied.
