Hello David. I am not sure this is a real issue since in SQL Server 2005 the max memory that the UDA can take up is 8k and if using the -1 MaxSize starting in SQL Server 2008 you still only get up to 2 GB. And yes, 2 GB is a lot but it is a constraint that is presumably less than the total amount of memory available to SQL Server. Also, with using the compression the memory usage will be less. Of course, as Adam pointed out it is possible to do this (Median) in straight T-SQL but I have also included "Geometric Average" and "Root Mean Square" Aggregates in my SQL# library and neither one needs to keep the entire set in memory so it doesn't matter how large the dataset is. And to your final point, I also think that Microsoft should include at least those two ("Geometric Average" and "Root Mean Square") if not all three as built-in Aggregates.