Physical processes proceeding in a biological tissue under laser irradiation are described. Based on evaluation of all heat-mass transfer processes, a model of biological tissue destruction is proposed as the multiboundaryvalue Stefan problem with stepwise variation of thermophysical parameters at phase boundaries. To check the model adequacy, a one-dimensional problem has been numerically solved which makes it possible to determine the dimensions of carbonization zones and the boundary velocities. Analysis of the results obtained allows a conclusion to be made about the model adequacy to real processes of biological tissue destruction.