In this paper we present a general theory for maximum likelihood infer
ence based on sample survey data. Our purpose is to identify and empha
sise the recurring basic concepts that arise in the application of lik
elihood methods, including the estimation of precision, to survey data
. We discuss the problems generated by the effects of sample design, s
election and response processes. We also discuss the problem of failur
es of the model assumptions and the role of sample inclusion probabili
ties in achieving robustness. We present two illustrative examples, on
e of which illustrates the use of non-Gaussian models.