WHERE THEY COME FROM
Viacom might not exist if the F.C.C. had permitted CBS to reap the limitless rewards of I Love Lucy and Honeymooners reruns. In 1971, after the feds ruled that networks couldn’t own the companies that syndicated their programs, CBS spun off its syndication division as Viacom. Over the next 15 years, Viacom picked up a handful of television and radio stations, including MTV. But it remained a modest media group until 1987, when a Boston businessman used a sizable chunk of the earnings from his family’s cinema chain to become Viacom’s majority shareholder. His name: Sumner Redstone.

WHAT THEY DO
With MTV shows including Total Request Live and My Super Sweet 16, Viacom fills the after-school time of teens—as it has since it bought the channel in 1985. Viacom’s other cable properties include Comedy Central, BET, and Nickelodeon. On the film side, it owns blockbuster heavyweight Paramount, which in turn owns DreamWorks.

WHAT THEY GOT RIGHT
Redstone famously goes with his gut—advisers and analysts are relevant only when their opinions mirror his own—and his aggressive moves have yielded key victories for Viacom.

The company has bet big on expansion. Redstone nurtured MTV into the world’s largest network by green-lighting spin-off channels and stations around the globe. Having enjoyed a lock on the youth audience since it changed the media landscape in the 1980s, MTV has made the transition from a Top 40 video format to one dominated by original programming—most notably, reality shows like The Real World.

Redstone moves quickly when opportunities arise. He bought Paramount in 1994 after a prolonged bidding war with Barry Diller, taking just four days to approve the strategy for an eleventh-hour clinching bid. In 2005, Paramount played the sharp lothario to Universal’s bumbling suitor in the fight for DreamWorks. In a week, Redstone procured the offer that made the studio swoon; G.E.’s Universal, which had wooed it for nine months, was left in the dust.

Redstone also led Viacom to a $39.8 billion reunion with CBS in 2000. The merger gave Viacom a majority interest in Infinity Broadcasting, CBS’s radio giant, and added TNN and CMT to the cable family. Then, at the close of 2005, Redstone reinstated the split, grouping cable and film entities under the Viacom banner and network and radio divisions under CBS. Redstone guessed the separation would free Viacom from CBS’s stagnant growth. He was right; by the end of Viacom’s second quarter after the split, the company’s stock was up 24 percent.

WHAT THEY GOT WRONG
Viacom is struggling with its new-media identity. Purchases like Neopets.com, an interactive pet site, and GoCityKids.com, a Citysearch for tykes, are relative unknowns. And MTV Overdrive, the network’s broadband video channel, hasn’t managed to catch on, despite appealing features like live-streamed after-shows and an online game linked to the popular Laguna Beach series. But Redstone is really fuming over Viacom’s failure to buy the already-hot internet property MySpace. Enraged by C.E.O. Tom Freston’s sluggishness in the race for the site, which ultimately went to Redstone’s nemesis Rupert Murdoch, Redstone replaced him with Philippe Dauman, who will seek to improve Viacom’s Web portfolio.

WHAT'S NEXT
He’ll have to work harder to integrate his most important purchase in recent history, DreamWorks SKG. A tug-of-war for creative control has gotten the Viacom-DreamWorks relationship off to a strained start—and since Viacom’s profits more than tripled after acquiring the studio, it’s in Redstone’s best interests to keep its top egos afloat. —Megan Angelo