A partial complement of the graph G is a graph obtained from graph G by complementing edges of some of its induced subgraphs. We study the following algorithmic question: for a given graph G and graph class G, is it possible to partially complement G to G? We show that this problem can be solved in polynomial time for various classes of graphs like bipartite, degenerate, or cographs. We complement these results by proving that the problem is NP-complete when G is the class of r-regular graphs.