Load tests were conducted on ten full-sized cast-in-place drilled caissons (bored piles, drilled shafts) of varying diameter. Three caissons were tested to evaluate end-bearing on the surface of fissile shale; five caissons were tested to evaluate side shear of shale sockets; one caisson was tested to evaluate end-bearing below weathered shale; and one caisson was tested to evaluate side shear in soil. Nine of the shale-bearing caissons tested exhibited subgrade failure, observed as excessive settlement, while the remaining shale-bearing caisson, drilled to end-bearing below the weathered shale, failed by shearing of the concrete shaft. The end-bearing test values exceed commonly employed empirical design values by factors ranging from 3 to 23. The shale sockets supported loads of at least one-third of and in some cases exceeding the ultimate end-bearing load.