Both experiments and numerical work are performed to study transient natural convection flow and transport process due to mass transfer in the enclosures inclined at different angles. In the experiments, the enclosure is filled with aqueous solution containing CuSO4 + H2SO4 where the flow structure can be visualized by both particle tracer and shadowgraph. Two opposed side walls of the enclosure are maintained at different concentrations which are made by passing current through the electrodes at the limiting condition. All the other side walls are made insulated and impermeable to the species transfer. Both the concentration distribution and its fluctuations are measured with non-intrusive optical method. During the experiments, the Rayleigh number ranges from 1.126 x 10(8) to 1.157 x 10(11), the angles of inclination from 30 to 90 degree and the aspects ratio of the enclosure from 0.6 to 1. Comparison between the data and prediction is made and discussed at various conditions. (C) 2008 Elsevier Ltd. All rights reserved.