Two-dimensional free convective heat transfer within an enclosure having a parallelogram shaped cross section and defined by two vertical walls of different temperatures and two oblique parting walls has been investigated. Two thermal conditions on the parting walls are considered namely, (1) linear temperature variation and (2) a perfect thermal insulator. Numerical computations are carried out for conditions: Prandtle number 0.72, aspect ratio 1, oblique angles -π/3 to π/3 and Rayleigh number 1 to 2×10⁶. Heat transfer coefficients on the hot wall are measured for air on the condition that the temperatures of the parting walls vary linearly and the experimental results agree with the numerical ones.