Magnetic properties of hole doped, oxygen deficient double perovskite compounds, Gd-1 (-) xCaxBaCo2O5.5. have been investigated. Ferromagnetic transition temperatures increase and the anti-ferromagnetic transition temperatures decrease with Ca substitution leading to stabilisation of ferromagnetisim for x >= 0.05. A detailed study of the ferromagnetic phase indicates the presence of double hysterisis loops for Ca fractions, 0.05 <= x <= 0.2 in the 50-200 K temperature range, suggestive of the co-existence of two ferromagnetic phases with different co-ercivities. Based on the magnetisationand transport measurements a phase diagram is proposed for Ca doped GdBaCo2O5.5. (C) 2012 Elsevier Ltd. All rights reserved.