Pressures and patterns for twelve male human buttocks and thighs in sitting in three different shaped seat pans were determined. Pressure was determined by multiple transducers situated geometrically on a conductive foam blanket which measured changes in resistance with an ohm meter as pressure was applied. The three chair seat pans consisted of a small round surgeons type stool, a standard biomechanic secretarial shaped chair, and a neutral posture chair which was a unique combination of a forward-sloping cultivator seat and an English saddle with wrap around leg trough support. Trunk-thigh posture angles of 90 and 127 deg for each chair were evaluated. The location of the maximum pressure points for all chair posture treatments had generally small tight patterns whose locations where consistent with the locations of the ischial tuberosities. The mean pressure was found to vary inversely with the total area. Thus, as the seat pan surface area decreased in total area in contact with the buttock-thigh, the larger the mean pressure became. Mean pressure values were also found to be in the same rank order and relative magnitude to subjective comfort for the buttock-thigh, conducted in related experiments on the chair-posture treatments. The neutral posture chair was found to reduce buttock-thigh maximum pressure from 118.94 mmHg (2.3 psi) to 62.06 mmHg (1.2 psi) and to reduce mean pressure by more than 50%.