Abstract. We show that Edge Dominating Set, Hamiltonian Cycle, and Graph Coloring are W [1]-hard parameterized by clique-width. It was an open problem, explicitly mentioned in several papers, whether any of these problems is fixed parameter tractable when parameterized by the clique-width, that is, solvable in time g(k) · n O(1) on n-vertex graphs of clique-width k, where g is some function of k only. Our results imply that the running time O(n f (k) ) of many clique-width based algorithms is essentially the best we can hope for (up to a widely believed assumption from parameterized complexity, namelyKey words. Parameterized complexity, clique-width, tree-width, chromatic number, edge domination, hamiltonian cycle AMS subject classifications. 68Q17, 68Q25, 68W401. Introduction. One of the most frequent approaches for solving graph problems is based on decomposition methods. Tree decomposition, and the corresponding parameter, the tree-width of a graph, are among the most commonly used concepts. We refer to the surveys of Bodlaender [3] and Hlinený et al. [22] for further references on tree-width and related parameters. In the quest for alternative graph decompositions that can be applied to broader classes than to those of bounded tree-width and still enjoy good algorithmic properties, Courcelle and Olariu [10] introduced the clique-width of a graph. Clique-width can be seen as a generalization of tree-width, in a sense that every graph class of bounded tree-width also have bounded clique-width [5].In recent years, clique-width has received much attention. Corneil, Habib, Lanlignel, Reed, and Rotics [4] show that graphs of clique-width at most 3 can be recognized in polynomial time. 3 ) and computing (2 k+1 − 1)-expressions for a graph G of clique-width at most k. It is also worth to mention here the related graph parameters NLC-width introduced by Wanke [30] and rank-width introduced by Oum and Seymour [27], which are equivalent to clique-width in the sense that the same classes of graph have bounded clique-width, NLC-width ans rank-width.By the seminal result of Courcelle [6, 9] (see also [1]), every decision problem on graphs expressible in monadic second order logic is fixed parameter tractable when parameterized by the tree-width of the input graph. For problems expressible in monadic second order logic with logical formulas that do not use edge set quantifications (so-called M S 1 -logic), it is possible to extend the meta theorem of Courcelle to graphs of bounded clique-width. As it was shown by Courcelle, Makowsky, and