Dry deposition and size-selected respirable particulate matter were simultaneously sampled on a daily basis at two locations, Shenzhen and Hong Kong, in April 1999. Ionic concentrations were generally similar at both locations, but with a greater abundance of crustal-derived ions at Shenzhen, and seasalt-derived ions at central Kowloon. Chloride depletion in the Hong Kong samples involved substitution by both nitrate and sulphate. The aerosol particle size distributions showed the presence of ammonium ion in the fine mode, and crustal and seasalt-derived ions in the coarse mode. Formic and acetic acids were roughly equally distributed between coarse and fine modes. Dry deposition fluxes in April are compared with annual means from Hong Kong Environmental Protection Department data, and dry deposition velocities are calculated. (C) 2001 Elsevier Science Ltd. All rights reserved.