An experimental study of low-level turbulence natural convection in an air filled vertical square cavity was conducted. The cavity was 0.75 m high x 0.75 m wide x 1.5 m deep giving 2D flow. The hot and cold walls of the cavity were isothermal at 50 and 10 degreesC respectively giving a Rayleigh number of 1.58 x 10(9). The local velocity and temperature were simultaneously measured at different locations in the cavity and both mean and fluctuation quantities are presented ,i.e. (u) over bar, u'(rms), (ν) over bar, nu'(rms), (T) over bar, T'(rms), (u'ν') over bar, (u'T') over bar and (ν'T') over bar. The local and average Nusselt numbers, the wall shear stress as well as the turbulent kinetic energy and the dissipation rate of the temperature variance are also presented. The experiments were conducted with very high accuracy and as such the results can form experimental benchmark data and will be useful for validation of computational fluid dynamics codes. (C) 2003 Elsevier Ltd. All rights reserved.