JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Biometrika Trust is collaborating with JSTOR to digitize, preserve and extend access to Biometrika. SUMMARY This paper generalizes the work of Godolphin (1977Godolphin ( , 1978 for estimating parameters of the moving average model and of the general autoregressive moving average model by solving the approximate log likelihood equation of Walker (1964).