In the spring of 1987, KLOS general manager Bill Sommers hired longtime rock radio programmer Charlie West to be the station's new program director. West hired Stephanie Mondello as music director for the station. By fall, West brought "Mark & Brian" (Mark Thompson and Brian Phelps) to KLOS for morning drive. The station's Arbitron ratings grew steadily under West's direction; by 1988, KLOS emerged as the leader among Los Angeles album rock stations, finishing fifth overall in the market with a 4.3 share, up from a 3.6 the previous ratings period. When West left KLOS in early 1989, Mondello assumed programming duties, directing all key decisions and overall revenue and ratings strategies. The station maintained its fifth-place ranking overall in the market and reached the number-one position in its target young male demographics, defeating main rivals KLSX, KROQ-FM, and the upstart KQLZ (Pirate Radio). Mondello left KLOS in late 1990.