In early 1979, after the stations were sold, the call letters were changed to WXKS and WXKS-FM, with the "KS" in the call letters representing the word "Kiss". Both stations launched a disco format (mostly, but not completely, simulcast), with the FM (Kiss 108) soon becoming one of Boston's most popular radio stations, although the AM had very few listeners. The FM side eventually made a very successful transition from disco to mainstream top 40; by that time, however, the AM no longer had the same format as the FM.
