A vertical multiple-effect diffusion solar still, consisting of a glass cover and a series of closely spaced vertical and parallel partitions in contact with saline-soaked wicks, coupled with a flat plate reflector was constructed and examined in outdoor experiments at Fukuoka, Japan. The vertical partitions make it possible to reduce the diffusion gaps between partitions to increase distillate productivity. The overall daily productivity of the proposed still with 6-effect and 5 mm diffusion gaps was about 13.3 kg/m(2) day at maximum when the global solar radiation on a horizontal surface was 13.4 to 15.7 MJ/m(2) day and radiation on the glass cover was 202 to 22.9 MJ/m(2) day. The productivity of the still would be greater than or approximately equivalent to other types of multiple-effect diffusion still. The discrepancy between experimental results and theoretical predictions was observed in several experiments, and a discussion on this discrepancy is also presented. (C) 2009 Elsevier B.V. All rights reserved.