Some years ago as part of a program for the investigation of compounds related to mephenesin (I, R= o-tolyloxy; R'= OH) and chlorphenesin (I, R= p-chlorophenoxy; R'= OH), the formally related 4-aryloxy-3-hydroxybutyric acids (I, R= o-tolyloxy or p-chlorophenoxy; R'= C02H) were prepared for routine biological screening.