[en] GeTe is an important phase change material lying on one end of the pseudobinary line of Ge-Sb-Te alloys, with Sb 2 Te 3 at the other end. The complex growth behaviour of ternary Ge-Sb-Te alloys requires better understanding of the binary component GeTe. Here, we report on the molecular beam epitaxy of GeTe on Si (111) substrates and the use of desorption mass spectroscopy as an in-situ technique for compositional analysis during the growth. The source fluxes of Ge and Te are kept at a ratio of 2: 5. The GeTe samples grown at different substrate temperatures were continuously monitored by a quadrupole mass spectrometer and an algorithm was made to subtract the observed background pressure, thereby deducing the incorporation ratio of various atomic species. With the assumption that the sensitivity of the mass spectrometer is one, we calculate the Te to Ge ratio of incorporating atoms. The compositional results lie within 10% of the values confirmed by XRF measurements. X-ray diffraction analysis was performed on the grown samples and the crystal structure was found to be hexagonal. We find that the growth of GeTe is independent of Te as long as there is an excess tellurium flux, which shows that GeTe behaves like III-V materials: with higher Te flux, the growth is Ge limited.