A relatively simple model, using Baker parameters, is described and applied to flow-regime data generated by high speed photography of two-phase steam flow. The experiments were conducted at the Geothermal Test Facility (GTF) at Lawrence Livermore Laboratory. Although results depend somewhat on the personal judgment and interpretation of the observer, the model was found to give a reasonable prediction of the flow regime for the flow ranges available in 1- and 2-in.-diam pipes.