Catholic News Service Classifications:

A-I -- general patronage;
A-II -- adults and adolescents;
A-III -- adults;
L -- limited adult audience, films whose problematic content many adults would find troubling.
A-IV* -- DISCONTINUED RATING. Originally adults, with reservations (an A-IV classification designates problematic films that, while not morally offensive in themselves, require caution and some analysis and explanation as a safeguard against wrong interpretations and false conclusions);
O -- morally offensive.

* Archived movies rated A-IV should now be considered as if rated L.

MPAA Ratings:

(Motion Picture Association of America)
G - general audiences, all ages admitted
PG - parental guidance suggested, some material may not be suitable for children
PG-13 - parents are strongly cautioned. Some material may be inappropriate for children under 13
R - restricted, under 17 requires accompanying parent or adult guardian
NC-17 - no one 17 and under admitted (age limit may vary in certain areas)