The overall technical objectives for the Phase 1 programme of the Grimethorpe Experimental Facility were presented in a draft document ''Phase 1 Research Programme: Baseline and Modified Option Cases'', produced in May 1979 and discussed at subsequent Technical Committee Meetings. The technical objectives for Test Series 1 presented in this document have developed from those outlined in the May 79 baseline; all the changes from the earlier outline are recorded. The data collection systems expected to be used are also presented. It is planned to carry out experiments to meet the objectives in three sub-series each along a different ''good fluidization''line determined at high, medium and low velocities. The high velocity sub-series has four runs including the original design conditions for Tube Bank 'A'. The medium velocity sub-series has seven runs and involves operating Tube Bank 'A'at what are to be its optimum operating conditions. The low velocity sub-series has six runs including the CURL Link Test operating conditions.