This paper investigates memory and selective repeat ARQ techniques when channels in both directions are very noisy. It demonstrates that a difficulty arises when memory ARQ is used in these situations, and proposes a remedy-the similarity test. The paper considers a combination of both memory ARQ techniques where an unacknowledged block is retransmitted exactly as before, and modified memory ARQ where alternate transmissions together form a rate 1/2 code. The following items are featured. 1) Discussion and analysis of the similarity test. 2) A memory ARQ technique which employs double null zone reception and 3 bits of past information storage per binary digit. 3) For modified memory ARQ procedures, a discussion of how to resolve problems of confusing the identity of the two halves of the rate 1/2 code used.