(001) surfaces of InP single crystals have been deformed at room temperature by a Vickers indentor submitted to a load of 1 N. The indents formed were observed by transmission electron microscopy (TEM) in cross-sectional views obtained by the focused-ion beam (FIB) technique. The structure of the plastic zone has been investigated and the different modes of plastic deformation involved during the deformation have been analysed. The flow stress of InP was estimated and compared to the reported values in the literature.