Physics of Stars and Interstellar Medium Ukrainian The inhomogenity of interstellar medium and anisotropic energy release during the outburst result in the nonsphericity of supernova remnants (SNRs) and in the difference in evolutionary stages of distinct parts of SNRs. We present the analytical description of 3D evolution of nonspherical SNRs in nonuniform medium, including adiabatic, transition and radiative stages. It is shown that in interstellar medium with large-scale density gradient and in case of anisotropic supernova outbursts the transition to radiative stage with the formation of a dense cold envelope takes place at different instants of time for different parts of the front surface. Therefore, such SNRs will simultaneously have sections in adiabatic, transition and radiative stages. The observable signatures of the SNRs of this kind are discussed. supernova remnant,evolution of supernova remnants