The effects of rib orientation to the direction of flow on the heat transfer performance of ribbed surfaces in forced convective boiling have been investigated experimentally. Test surfaces were manufactured from a stainless steel plate of 1.60 mm thickness on to which transverse rectangular ribs were machined. Rib height, length and spacing were kept constant at 0.50 mm, 1.00 mm and 0.50 mm respectively and rib orientation to the direction of Bow was varied from 0 degrees to 135 degrees. In order to ensure good reproducibility of the experimental data, the effects of surface roughness were isolated by providing a constant surface micro-roughness for all test specimens and the effects of aging were also isolated. Experimental data are reported for heat transfer from ribbed surfaces to water boiling at atmospheric pressure for velocities ranging from 0.2 m/s to 1.4 m/s and inlet subcoolings from 5 degrees to 30 degrees C.