Reflectance anisotropy spectroscopy (RAS) and Raman scattering are presented as in situ and online analytical tools for epitaxial growth of semiconductors. While RAS derives its surface sensitivity from an anisotropic surface structure, Raman scattering has monolayer resolution at heterointerfaces due to the fingerprint character of the vibrational properties of the overlayers. The growth examples discussed are MOVPE growth of GaAs on GaAs analysed by RAS and MBE growth of InSb on Sb as well as CdTe on InSb monitored by Raman scattering. The information gained concerns the status of the pregrowth surface (RAS), growth rate with monolayer resolution (RAS), growth morphology (Raman scattering) and the detection of interface reactions (Raman scattering). Both methods can be applied with a time resolution of a few seconds (Raman scattering) or better (RAS).