High-spin states in 169, 170W have been populated in 154 Gd( 20 Ne, x n) reactions. In-beam γ-ray spectroscopic techniques with multi-detector set-ups, multiplicity filters and an anti-Compton shield have been used. Levels up to about spin 30 (tentatively up to 36) in 170W and up to 57 2 (tentatively up to 61 2 ) in 169W have been identified. The data are interpreted within the framework of a pairing-selfconsistent cranking model. The nuclear shape evolution with increasing spin is studied theoretically within a configuration-controlled shell correction approach and also pairing effects are studied. The behaviour of the yrast states around 28 + in 170W can be related in a model-dependent way to a reduction of the neutron-pairing correlations.