[en] The mass dependence of the chiral phase transition is studied in the linear SU(3)_LxSU(3)_R Sigma model to leading order in a 1/N_f-expansion with N_f denoting the number of flavours. We find a smooth crossover about T ∼185 MeV for realistic meson masses. The crossover looks more rapid in the light quark condensate than in thermodynamic quantities like the entropy densities. Since the numerical error is particularly large in this region, wecannot rule out a finite latent heat smaller than 0.2 Gev/fm³. The ratio of critical to realistic light current quark masses m_u,d^crit/m_u,d is estimated at 0.26±0.08. This result is by an order of magnitude larger than the corresponding mean-field value. (orig.)