The asymptotic properties of four estimators for nonlinear mixed-e¤ects models are investigated: maximum likelihood estimator (MLE), an estimator based on the ...rst-order approximation to the expectation function (Vonesh and Carter (1992)), the two-stage, and the Lindstrom-Bates (1990) estimators. Two asymptotic situations are considered: (i) when N ! 1 and ni is ...nite, (ii) N ! 1 and minni ...