  We study phase transition of self-avoiding fluid surface model on dynamically
triangulated lattices using the Monte Carlo simulation technique. We report the
continuous transition between the branched polymer and inflated phases at ${\it
\Delta}p \!=\!0$, where ${\it \Delta}p (=\!p_{\rm in}\!-\!p_{\rm out})$ is the
pressure difference between the inner and outer sides of the surface. This
transition is characterized by almost discontinuous change of the enclosed
volume versus the variations of the bending rigidity $\kappa$ and the pressure
difference ${\it \Delta}p$. No surface fluctuation transition accompanies this
transition up to the surface with the number of vertices $N\!=\!2562$.
