Upgrading from:

Statistics`MultiDiscreteDistributions`

Distributions defined in this package are included in the newly created Multivariate Statistics Package.
Random and RandomArray are replaced by RandomInteger.
CovarianceMatrix and CorrelationMatrix are replaced by Covariance and Correlation.

Load MultivariateStatistics` to use Multivariate Statistics Package functionality:

Version 5.2 << Statistics`MultiDiscreteDistributions`; PDF[MultinomialDistribution[10, {1/5, 3/10, 1/2}], {3, 4, 3}]

Random elements for multivariate discrete distributions are generated via RandomInteger:

Version 5.2 << Statistics`MultiDiscreteDistributions`; Random[MultiPoissonDistribution[10, {1, 2, 3}]]
Version 5.2 << Statistics`MultiDiscreteDistributions`; RandomArray[MultiPoissonDistribution[10, {1, 2, 3}], 5]

Covariance matrix for a multivariate distribution:

Version 5.2 << Statistics`MultiDiscreteDistributions`; CovarianceMatrix[MultiPoissonDistribution[10, {1, 2, 3}]]