Began his film career as a prop boy for
D.W. Griffith and moved on to photograph
and direct at the
Hal Roach studios, where he met another upcoming
cameraman/director,
George Stevens; both men worked on many of the best
Stan Laurel and
Oliver Hardy silent shorts. When Stevens moved on to RKO in the
sound era, Guiol went with him. Unfortunately, many of the "B" films Guiol
directed there did not make money. Stevens, however, never forgot him,
hiring him as a screenwriter on
Gunga Din (1939), associate producer on
Ho sognato un angelo (1941) and
Molta brigata vita beata (1943), producer of
Un evaso ha bussato alla porta (1942) and associate director on
Un posto al sole (1951) and
Il cavaliere della valle solitaria (1953). In 1956 Guiol shared an Academy Award nomination for his screenplay on Stevens'
Il gigante (1956).