A wind turbine blade comprising an elongate spar (6). A first plurality of skin panels (1) are attached in an upper high pressure row to the spar to form a substantial proportion of the external profile of one surface of the blade. A second plurality of skin panels (1) are attached in a lower low pressure row to the spar to form a substantial proportion of the external profile of the opposite lower surface of the blade. A plurality of the skin panels in each row are each integrally provided with a bulkhead (2) which supports the skin panel on the spar.