  A sample of hundreds of simulated galaxy clusters is used to study the
statistical properties of galaxy cluster formation. Individual assembly
histories are discussed, the degree of virialization is demonstrated and
various commonly used formation times are measured and inter-compared. In
addition, the fraction of clusters which have ``recently'' undergone a major
merger or significant mass jump is calculated as a function of lookback time
and interval. The fraction of three- and four-body mergers is also studied.
