This article describes experimental investigations of two-phase flow regimes for steam-water flowing in horizontal ducts of small diameters. In this respect two-phase flow patterns are determined on a test stand based on visualization of real flows. Measurements were performed for a round tube with an internal diameter of 2.8 mm under mass flux ranging from 160 kg/s-m(2) to 1600 kg/s-m(2) at saturation temperatures between 373 K and 403 K. Registered steam quality varied from 0.02 to 0.27. Experimental setup, methodology, and recorded two-phase flow patterns referenced to annular, intermittent, and transient flows are presented. The results obtained have been compared with annular to wavy transition criteria described on the flow map by Soliman.