A glass of the BiSrCaCuO superconducting system with nominal (Bi1.0Tl0.5Ga0.5)Sr2Ca2Cu3O10+y composition has been prepared by the melt-quenched method. The crystallisation kinetics of the glass was investigated using non-isothermal analysis. The activation energy for crystallisation was found to be 420.6Kjmol(-1). The Superconducting transition and zero resistance temperatures were T-c=118.8K and T-zero=114.6K respectively. The calculated critical current density was J(c)=8.85x10(6) Acm(-2) at 4.5K, In general, substitution of both Tl+3 and Ga+3 for Bi+3 increased the activation energy for crystallisation and enhanced the superconducting phase formation. (C) 1997 Academic Press Limited.