To provide a comparison of the contents of subcutaneous and deep bursae we dissected these structures from unfixed cadavers without apparent joint disease. No free fluid was found within any olecranon or prepatellar bursae (examples of subcutaneous bursae), while viscous fluid was invariably present in the (deep) retrocalcaneal bursae. The hyaluronic acid content of the washings of 5 rectrocalcaneal bursae ranged from 142 to 591 nmol hexosamine (mean = 281 nmol hexosamine). In contrast, the hyaluronic acid content of 4 olecranon bursae was much lower (range 35-72 nmol, mean 53 nmol hexosamine), and hyaluronate was not detected in washings from either of 2 prepatellar bursae. The greater hyaluronate content of the retrocalcaneal bursae did not appear to be due to a greater surface area, since on the basis of calculations made from plaster casts the surface areas of the olecranon and prepatellar bursae were approximately 3 times and 2 times, respectively, greater than that of the retrocalcaneal bursae. The data suggest that, although hyaluronic acid may lubricate deep bursae, other factors may be more important in reducing friction within superficial bursae.