Natural convective boundary layer flow and heat and mass transfer of a fluid with temperature-dependent fluid viscosity, chemical reaction and thermal radiation over a vertical stretching surface in the presence of suction is investigated by scaling transformation analysis. Fluid viscosity is assumed to vary as a linear function of temperature. The symmetry groups admitted by the corresponding boundary value problem are obtained by using a special form of Lie-group transformations viz, scaling group of transformations. An exact solution is obtained for translation symmetry and numerical solutions for scaling symmetry. Effects of temperature-dependent fluid viscosity, chemical reaction and thermal radiation on the dimensionless velocity, temperature and concentration profiles are shown graphically. Comparison with previously published work is performed and excellent agreement between the results is obtained. The conclusion is drawn that the flow field and temperature and concentration profiles are significantly influenced by these parameters. (C) 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.