Abstract. Let R(n) denote the number of representations of a large positive integer n as the sum of two squares, two cubes and two sixth powers. In this paper, it is proved that the anticipated asymptotic formula of R(n) fails for at most O((log X) 2+ε ) positive integers not exceeding X. This is an improvement of T. D. Wooley's result which requires O((log X) 3+ε ).