In the first episode of HBO’s “epic seven-part miniseries event” “John Adams,” one of the most riveting scenes occurs at Boston Harbor, when a customs inspector or informant challenges John Hancock (Justin Theroux) for evading the taxes imposed by the British. “Teach him a lesson, tar the bastard,” Hancock commands a mob, which proceeds to do exactly that to the poor accessory of the crown. This being HBO, there’s a glimpse of full frontal nudity that is promptly drenched with hot tar. Hancock looks on, as do John Adams (Paul Giamatti) and his cousin Samuel (Danny Huston). “God, Sam, that’s barbarism,” John cries to his cousin, who stands silent. “Do you approve of this? Answer me, Sam, can you?”

It’s a telling scene, because there is no historical evidence that it ever happened. It’s not included in the Pulitzer Prize-winning biography of our second president by David McCullough, upon which HBO’s miniseries event, which makes its premiere Sunday at 8 p.m., claims to be based. It’s not included in James Grant’s biography of John Adams, “Party of One,” nor in any of the many biographies of Samuel Adams. There was a riot in June of 1768 over Hancock’s ship, the Liberty, in which customs officials were beaten, but there is no evidence that Hancock or either Adams was at the scene of that riot, nor is there any record that anyone was tarred in the event. One historian who examined the subject recently, Alfred Young, found that there were only three individuals subject to “full-scale tar and featherings in Boston in the revolutionary era,” and that “In Boston, Whig leaders” — of whom Hancock and both Adamses were certainly at the forefront — “invariably were hostile to tar-and-feathering; they tried to rescue the victims.”

The scene does convey, accurately, John Adams’s hostility to mob violence. “These private Mobs, I do and will detest,” he wrote to his wife Abigail on July 7, 1774. “These Tarrings and Featherings, these breaking open Houses by rude and insolent Rabbles, in Resentment for private Wrongs or in pursuance of private Prejudices and Passions, must be discountenanced.” But it does so by inaccurately, well, tarring the reputations of Hancock and Samuel Adams, and by conjuring a situation that there is no evidence existed.

Such are the compromises attendant in turning history into a seven-part miniseries for television. As Mr. McCullough himself acknowledges in publicity material for the epic miniseries event, “A great film production involving the efforts of hundreds, even thousands, of people, as this has, is a vastly different undertaking from that of an author setting out to write a book. The medium itself is infinitely different from that of the printed page and a multitude of different considerations have to be weighed and decided on.”

Mr. McCullough is so deservedly celebrated as an author not only for his skill as a storyteller but for his care with research and facts. So it is disappointing to see the television version of his bestselling biography make such departures. In another particularly gory and memorable moment, we see Abigail Adams (Laura Linney) and her children inoculated against smallpox. Mr. McCullough’s book recounts the procedure happening in Boston, while the epic miniseries event portrays it as happening at the Adamses’ Braintree farmhouse.

If the lack of footnotes in television makes such inaccuracies hard for most casual observers to trace or detect, the medium does have its advantages. It makes the experience of life during revolutionary times immediate and vivid. When Adams assists in a shipboard amputation — as he really did — you see the blood spurting. As Adams, Mr. Giamatti’s face expresses the frustration that the Massachusetts delegate to the Continental Congress in Philadelphia felt at the caution and conciliation counseled by delegates from places such as Pennsylvania and New York, and it conveys the exasperation Adams the New Englander felt at the degree to which Benjamin Franklin (Tom Wilkinson) immersed himself during wartime in the pleasures of Paris. As Abigail Adams, Ms. Linney shows us the difficulty of being separated from her husband for long stretches.

The HBO series goes to great lengths in some measures to achieve historical accuracy, or at least verisimilitude. Press materials boast of a budget of more than $100 million, more than 5,700 extras, historical researchers from Colonial Williamsburg to instruct actors on period etiquette, and a set with 250,000 cobblestones, 1,500 wigs, 40 working fireplaces, and 43 fake cannons that weighed 800 pounds each. Some of the dialogue is indeed taken from Adams’s own writings.

If all that adds up to make viewers think what they are seeing on television is what really happened rather than an epic miniseries event, they will have been duped. On the other hand, they may well be entertained and intrigued enough by the drama and ideas of Adams’s life and time to investigate further. They can do so by reading Mr. McCullough’s book or Mr. Grant’s. Or by going to the Web site of the Massachusetts Historical Society and browsing Adams’s diary or the correspondence he had with Abigail, some of which will be on display between April 5 and April 30 at the Vassar College library in Poughkeepsie, N.Y.. In that case, they will be on their way to distinguishing for themselves the difference between history and an “epic seven-part miniseries event.”

Mr. Stoll’s biography of Samuel Adams is forthcoming from Free Press.