Abstract The defect structure in epitaxial silicon films grown by solid phase epitaxy (SPE) and by molecular beam epitaxy (MBE) has been studied by probing with implanted helium. It was found that SPE layers contain large vacancy clusters (voids) at a low density. In both SPE and MBE films, other not yet fully identified but smaller defects which trapped helium were detected. The detection of voids is in agreement with results of cross-sectional transmission electron microscopy observations of the SPE film. Defect concentrations found in the SPE and MBE films are similar to earlier results obtained with positron beam analysis on these layers.