SUMMARY This paper shows a method to represent interval functions by using head-tail expressions. The head-tail expressions represent greaterthanGT(X : A )f unctions,less-than LT(X : B )f unctions, and interval functions IN0(X : A, B )m ore efficiently than sum-of-products expressions. Let n be the number of bits to represent the largest value in the interval (A, B). This paper proves that a head-tail expression (HT) represents an interval function with at most n words in a ternary content addressable memory (TCAM) realization. It also shows the average numbers of factors to represent interval functions by HTs for up to n = 16, which were obtained by a computer simulation. It also conjectures that, for sufficiently large n, the average number of factors to represent n-variable interval functions by HTs is at most 2 n − 5 .E xperimental results also show that, forn ≥ 10,