1. The inbred strain of mouse is a relatively inexpensive and easily controlled animal that produces consistent results within each of the P1, P2, F1, F2, B1 and B2 generations. 2. The mother and father exert an equal influence on the development of fatty deposits in the aortic sinus wall and on serum total cholesterol levels. 3. Different strains of inbred mice react to the high-fat, high-cholesterol diet in different ways. 4. The control mice of the CBA/J (P2) strain had significantly lower values of serum total cholesterol and size of the largest lesion at some weeks than the control mice of the C57BR/cdJ and F1, F2, B1 and B2 generations. 5. The experiments indicate a multifactorial (polygenic) system of inheritance.