In 1964, Wilhelm finished with career highs in both saves (27) and games pitched (73). His ERA decreased to 1.99 that season; it remained less than 2.00 through the 1968 season. In 1965, Wilhelm contributed to another passed balls record when Chicago catcher J. C. Martin allowed 33 of them in one season. That total set a modern single-season baseball record for the category. Wilhelm's career-low ERA (1.31) came in 1967, when he earned an 8–3 record for the White Sox with 12 saves.