Using an optimized procedure, large SAPO-5 single crystals (up to 250 X 75 mu m) with a very high optical quality could be synthesized. NMR spectroscopy proved the perfect incorporation of silicon on phosphorus sites. IR microscopy with polarized IR radiation revealed that both types of OH groups, with absorption bands at 3627 and 3519 cm(-1), ate oriented almost perpendicularly to the crystal c-axis, thus protruding into the 12-membered and the 6-membered ring channels, respectively. Adsorbed p-xylene reacts with both types of OH groups, giving rise to one broad band for the OH vibration at 3233 cm(-1), which indicates a-shift of the proton from the 6-membered ring to the 12-membered ring. From the dichroic ratios of the bands due to the p-xylene, it can be inferred that the long axis of the p-xylene molecule is oriented parallel to the channel axis of the molecular sieve.