A semi-algebra of continuous functions is a cone$A$ of continuous real functions on a compactHausdorff space $X$ such that $A$ contains the products of its elements. A cone $A$ is said to be of type $n$ if $f\in A$ implies$f^n(1 + f)^{-1} \in A$. Uniformly closedsemi-algebras of types 0 and 1 have long beencharacterized in a manner analogous to the Stone--Weierstrass theorem, but, except forthe case when $A$ is generated by a singlefunction, little has been known about type 2.Here, progress is reported on two problems.The first is the characterization of those continuous linear functionals on $C(X)$ that determine semi-algebras of type 2. The secondis the determination of the type of the tensorproduct of two type 1 semi-algebras. 1991 Mathematics Subject Classification: 46J10.