Polycrystalline Bi2Sr2MnO6+delta samples were subjected to a high pressure-high temperature process and the effects on crystal structure and magnetic properties recorded. The unit cell was found to expand anisotropically with the c axis length increasing at four times the rate of the a and b axes where (da/dP) = (db/dP)= 1.0 +/- 0.2 x 10(-3) Angstrom MPa(-1) and (dc/dP) = 3.5 +/- 0.5 x 10(-3) Angstrom MPa(-1) with an overall unit cell volume expansion of 1%. The net oxidation state of the manganese decreased from +3 towards +2 with a resultant increase in T-N. These changes can be attributed to the effect of removing interstitial oxygen from the structure which primarily changes the oxidation state of the manganese.