European companies have long understood the value of custom magazines, employing them as relationship marketing tools, with content designed to appeal to the interests of readers rather than as vanity pieces for the marketer. While some companies in this country have been successfully using custom magazines for decades, their widespread use is an exciting new addition to the marketing mix of U.S. corporations. Growing numbers of the nation's top firms in healthcare, finance, technology, fashion, entertainment, travel and consumer products are embracing this effective communications medium. Custom publications have grown to 13.2% of an average firm's marketing and communications expenditures, up from 11.1% in 2000, according to a recent survey of Publications Management, a periodical of the custom publishing industry.