The samples came from the William F. McCormick collection at the University of Tennessee in Knoxville. The sample included juveniles and adults ranging in age from 10 to 92 years. Results of logistic regression analysis revealed significant relationships between the presence of a rhomboid fossa and sex as well as between the presence of a rhomboid fossa and age. Fossae were more common in males (36 percent left, 31 percent right) than in females (3 percent left, 8 percent right). Posterior probabilities suggested that a fossa on the right clavicle is indicative of a male with 81.7 percent probability; a fossa on the left is indicative of a male with 92.2 percent probability. Younger individuals more commonly exhibited rhomboid fossae than did older individuals; the largest fossae were most common in males 20-30 years of age. However, the age effect was not conclusive and requires corroboration by other methods. A test of the sex estimation method on an independent sample of 26 males and 23 females revealed that 9 males and only 1 female had fossae present on the left clavicle. Findings indicated that this technique can corroborate other sex estimates or can provide an estimate for unknown individuals in the absence of other skeletal indicators. Figures, photographs, tables, and 16 references (Author abstract modified)