This Resource Letter provides a guide to the literature on the foundations of quantum mechanics over approximately the past 20 years. Topics covered include Bell’s theorem, interpretation of the quantum state concept, the theory of measurement, and experimental tests of fundamental aspects of the quantum theory of matter and the electromagnetic field. The letter E after an item indicates elementary level of material of general interest to persons becoming informed in the field. The letter I, for intermediate level, indicates material of somewhat more specialized nature; and the letter A indicates rather specialized or advanced material. An asterisk (*) indicates those articles to be included in an accompanying Reprint Book.