The defending champions of the Friends Provident Trophy, Essex, have been placed in Group D of next year's tournament, along with Glamorgan, Lancashire, Derbyshire and Northamptonshire.
Last year's finalists, Kent, have been grouped with Warwickshire, Middlesex, Somerset and one of the two Associates, Scotland. Both Ireland and Scotland were pre-allocated to groups A and B respectively.
Sides will play the other four in their group home and away - a total of eight group matches each. The top two teams in each group will progress to the knockout quarter-final stage.