The growth by molecular beam epitaxy of GaAs and GaAlAs is reviewed, with special attention given to morphological defects which can occur. Although the allowed stoichiometric growth regime for this system is quite wide, more restricted conditions are required when overall perfection is important. The paper characterizes the growth process within the framework of achieving material suitable for GaAs–GaAlAs double heterostructure lasers. This includes substrate preparation, growth initiation, and growth evolution. Specific morphological defects which are found to be observed quite generally are characterized and some explanations will be ventured. Achieving featureless growths is important for integrated optic devices and this is possible over large area substrates.