OXFORD - One element of the hype surrounding American Home Products Corp. and Monsanto Co.'s merger agreement as a huge biotech opportunity rings especially true: as in most biotech stories, any major value addition to shareholder fortunes is likely to be in the long term rather than the near term.

With mega-mergers back in favor in the late '90s, the questions raised about conglomerates several decades ago by now may have been forgotten. One of the central issues raised by those earlier mega-companies is whether combining disparate businesses under one roof resulted in cost savings, cross-fertilization and synergies, or whether the conglomerates were merely reflections of a shared ownership without any particular value added.