The MIXED procedure effectively performs the same analyzes as PROC VARCOMP and many others, including Type I, Type II, and Type III tests of fixed effects, confidence limits, customized contrasts, and least squares means. Furthermore, continuous variables are permitted as both fixed and random effects in PROC MIXED, and numerous other covariance structures besides variance components are available. The VARCOMP procedure is more computationally efficient for some special designs and models.

To translate PROC VARCOMP code into PROC MIXED code, move all random effects to the RANDOM statement in PROC MIXED. For example, the syntax for the example in the section Getting Started: VARCOMP Procedure is as follows:

proc mixed;
   class Temp Lab Batch;
   model Cure = Temp;
   random Lab Temp*Lab Batch(Lab Temp);
run;

REML is the default estimation method in PROC MIXED, and you can specify other methods by using the METHOD= option.