An iron/gas parallel plate volume calorimeter prototype, working in the avalanche mode, has been tested using electrons of 20 to 150 GeV/c momentum with high voltages varying from 5400 to 5600 V (electric fields ranging from 36.0 to 37.3 kV/ cm), and a gas mixture of CF 4/ CO 2 (80%/20%). The collected charge has been measured as a function of the high voltage and of the electron energy. The energy resolution has also been measured. Comparisons have been made with Monte Carlo predictions. Agreement between data and simulation allows the calculation of the expected performance of a full size calorimeter.