Studies carried out have been directed toward (a) an examination of the nature of blood flow distribution within the skin and (b) a study of participation of superficial dermal capillaries in major changes of skin blood flow rate. This report consists of four Parts. Three Appendixes contain technical details of equipment construction and development. Part 1 contains a statement of objectives and a section on background. Part 2 is a summary of preliminary work including initial hypotheses and development of methods, and also describes preliminary work with helium transfer through the skin as an index of effective skin blood flow. The development of equipment and procedures for continuous analysis of helium at a sensitivity about six orders of magnitude is discussed in Part 3. Part 4 contains a general discussion of results, including comparison of data, on the relation of helium leak rate to skin temperature and calculations of skin blood flow required for maintaining constant core and skin temperatures.