We provide a collision attack and preimage attacks on the MDC-2 construction, which is a method (dating back to 1988) of turning an n -bit block cipher into a 2n -bit hash function. The collision attack is the first below the birthday bound to be described for MDC-2 and, with n = 128, it has complexity 2124.5, which is to be compared to the birthday attack having complexity 2128. The preimage attacks constitute new time/memory trade-offs; the most efficient attack requires time and space about 2 n , which is to be compared to the previous best known preimage attack of Lai and Massey (Eurocrypt '92), having time complexity 23n /2 and space complexity 2 n /2, and to a brute force preimage attack having complexity 22n .