Entering and editing mathematical equations on a computer can be difficult. Students may have to use a nonstandard notation which differs from that seen in their textbooks, thus adding to their confusion. Nakayama describes a program, called the Mathematical Formula Editor (MFE), which can be incorporated into programs for computer-assisted instruction (CAI) to provide an easy-to-use equation editor that also displays equations using conventional mathematical notation. Furthermore, it stores the equation in a tree-structured character string which may be analyzed by the CAI program. The MFE is written in C and assembly language and has been ported to several microcomputers including the IBM PC and PS/2. Although Nakayama recommends the editor for use with students in lower grades this paper only provides preliminary, although promising, results from a study done with 17–18 year olds. Despite this minor criticism the MFE appears to offer some benefits. It does not force users to learn a nonstandard notation, and it may be easier to learn than other editors, such as T2EX. In addition, it could save developers of CAI software the trouble of having to develop their own equation editors and display routines. This article should interest those who are involved in entering and displaying mathematics on a microcomputer, especially in CAI.