Abstract: A pharmaceutical composition comprises a solution or suspension of a biological agent in a diluent comprising D.sub.2 O, which solution or suspension contains sufficient amounts of a sugar, phosphate, glutamic acid or a physiologically acceptable salt thereof and, optionally, a non-toxic protein, a peptone or a mixture of two or more amino acids besides glutamic acid to enhance the stability of the agent. Typically, the composition is a suspension of a live attenuated poliovirus or an inactivated poliovirus of each of poliovirus types 1, 2 and 3. Preferably the solution or suspension contains stabilising amounts of sucrose, KH.sub.2 PO.sub.4, K.sub.2 HPO.sub.4, L-glutamic acid or sodium glutamate and human serum albumin (SPGA).