Weisberg was a strong critic of the Warren Commission report and of the methods used in investigating President Kennedy's murder. In this regard, he was avant-garde, embarking on a course that many other conspiracy theorists would later come to follow. Weisberg is best known for his seminal work, Whitewash, where he wrote: "Following thousands of hours of research in and analysis of the vast, chaotic, deliberately disorganized, padded and largely meaningless 26 volumes of the testimony and exhibits of the President's Commission on the Assassination of President John F. Kennedy and its 900-page Report – millions of words of which are not needed and are merely diversionary – I published the results of my investigation in a book, Whitewash: The Report on the Warren Report. In this book, I establish that the inquiry into the assassination was a whitewash, using as proof only what the Commission avoided, ignored, misrepresented and suppressed of its own evidence