The IOR/Hab inbred mouse strain, developed and maintained in the National Institute of Oncology and Radiobiology, is the first inbred strain to be developed in Cuba. It has a high fertility in this tropical climate. A number of physiological characteristics such as longevity, haematological characteristics, and growth are reported. Other experiments and results concerning spontaneous tumour frequency suggest that the strain is well adapted to standard environmental conditions, and could be useful for biomedical research.