Currently, PROC MDC does not provide a WEIGHT or FREQ statement. If you want to specify the number of times an observation is observed, then you will need to expand your data to have a separate row for each of the identical observations. That is, if an observation has a frequency of three, you should produce a total of three replicates of the observation. In this way, the likelihood contribution for the observation is effectively multiplied as would be done by a WEIGHT or FREQ variable. General weighted analysis, in which noninteger weights may be specified, is not available.