This report presents the rationale and design of a vocabulary program created as the instrument for research exploring the relationship between vocabulary knowledge and reading comprehension. The first section of the report reviews the current state of the art of vocabulary instruction and discusses the techniques used in two commercial basal reading series to teach vocabulary. The second section presents the rationale and theoretical positions underlying the experimental vocabulary program, while the third section details the structure of the program and presents examples of the types of instruction used in it. The final section briefly outlines the results produced by using the program in one fourth grade classroom. (FL)