In this paper, it is shown that for any pair of integers (m, n) with 4 <= m <= n, if there exists an m-cycle system of order n, then there exists an irreducible 2-fold m-cycle system of order n, except when (m, n) = (5, 5). A similar result has already been established for the case of 3-cycles. (C) 2005 Wiley Periodicals. Inc.