where H(D) denotes the set of all holomorphic functions on D. In case that i'{z) = 1 for every :eD we simply write and obtain the classical composition operator. Such operators have been investigated on various spaces of holomorphic functions and by several authors, see e.g. [17], [8], [13], [4], [6], [5], [11]. In this paper we are interested in operators acting between different weighted Bloch type spaces. For a continuous, strictly positive and bounded function ( weight ) on D we say that the weighted Bloch type space Bv is the collection of all holomorphic functions / on O such that