Abstract. The main purpose of this paper is to investigate some topological properties of the double multiplier algebra on a topological algebra. Let M d (A) be the double multiplier algebra on a topological algebra A, and let u and s be the uniform and strong operator topologies on M d (A), respectively. It is shown, under some additional hypotheses on A, In view of the applications of (nonnormed) topological algebras in other fields such as quantum mechanics and quantum statistics (see, e.g., Lassner [10,11]) and recent developments in the theory of topological algebras (see, for instance, the book of Mallios [13]), it is important to consider operators on more general classes of topological algebras. More recently, Phillips [14,15] has studied inner and approximately inner derivations on pro-C * -algebras (inverse limits of C * -algebras, also called LMC * -algebras) using multipliers, while Van Daele [20] has considered multipliers on Hopf algebras which provide a natural framework to study quantum groups. Therefore, it is important to develop the theory of multipliers for general topological algebras and, in particular, for metrizable topological algebras.In this paper, we are mainly concerned with the linear topological properties of