Top law firms grew by leaps and bounds in 2006. But one expense reportedly rose about 30 percent from the previous year, far outstripping growth in either profits or revenues: marketing.

Am Law 100 firms budgeted an average of $9 million — or 2.2 percent of their gross revenue — for marketing last year, according to a new survey by Boston-based BTI Consulting Group that polled about 60 percent of Am Law firms.