I have a small table of data:

Start End Appointment Date
11-Sep-09
26-Feb-10
26-Apr-10
10-Jun-09 12-Mar-10
10-Jun-09 26-Apr-10
10-Jun-09 12-Nov-09 11-Sep-09
10-Jun-09 12-Nov-09 12-Nov-09
06-May-10 06-May-10

I am tring to find the maximum date for each combination of start/stop.
Applying a max function to the appointment date in a query returns just two
records, not four

Start End MaxOfAppointment Date
10/06/2009 26/04/2010
10/06/2009 12/11/2009 12/11/2009

The minimum function returns four rows and it all seems correct for min?!
Why is this not working for Max please?