The scientific and methodological manual contains a brief history of the development of a methodology for testing micronuclei and nuclear anomalies in the erythrocytes of fish, amphibians, reptiles and birds. The morphological characteristics of 2 types of micronuclei and 23 types and subtypes of nuclear anomalies that can be detected during spontaneous and induced mutagenesis are described. The described anomalies are illustrated by microphotographs and schematic drawings. An algorithm for detecting anomalies and a template for their recording during microscopic analysis are presented. The scientific and methodological manual is intended for graduate students and researchers who study the influence of various factors on the stability of the genome of non-mammalian vertebrates.