We have carried out an investigation of the use of phosphosilicate glass (PSG) flow for integrated optical circuits. PSG layers of thicknesses ranging from 4 to 22 μm were chemically vapor deposited on V‐grooves in silicon substrates having a depth of 175 μm. The effect on the flow of (1) P2O5concentration in PSG layers (5–10 mol %), (2) ambient during flow (dry O2, wet O2, POCl3, and wet N2), (3) temperature (1000°–1200°C) and (4) time (30–120 min) of the process has been determined. The extent of flow, as measured by curvature of the rounded corners, has been plotted against PSG layer thickness and reflow time. Radii of curvature up to 36 μm through 70° bends have been measured.