Firemen's Ball and Oratorio for Prague--Two first rate, if lightweight, Czech films which run amuck. In Milos (Loves of a Blonde) Forman's comedy, the dramatic action edges toward the consequential and finally becomes downright grisly, with no let-up in the constant low-key joking. In Jan Nemec's documentary, reality gets out of hand as the appearance of Russian tanks drastically alter what had been intended as a cheerful film about the liberalized Dubcek regime. At the EXETER, Exeter St. between Commonwealth & Newbury (536-7067).

The Graduate--Mike Nichols' film about where Joe DiMaggio went. Too big for its britches. At the PARK SQUARE CINEMA, 31 St. James Ave. (542-2220).

Flea in Her Ear--The Georges Feydeau farce, butchered in this Jacques Charon film. Rex Harrison, Rosemary Harris, Rachel Roberts and Louis Jourdan are stuck in it. At the CINEMA KENMORE SQUARE (262-3799).

Funny Girl--If you like Barbra Streisand, there is no getting around the fact that this movie works. The score, the screenplay, and even Omar Sharif are fine. The photography, on the other hand, is unfortunate, as is the editing. At the CHERI 2, Dalton St. in Prudential Center (536-2870).

D.W. Griffith Films--Some short and early works. At CARPENTER CENTER, Sunday.

Great Catherine--Peter O'Toole is wonderful in this movie that goes wildly and badly off track about five minutes after it begins. Jeanne Moreau and Jack Hawkins do what they can to help things along, but Zero Mostel turns in a performance that is too undisciplined, qrotesque and awful to be believed. At the CHERI 3, Dalton St. in Prudential Center (536-2870).

Heart is a Lonely Hunter--Pretty weighty stuff from the Carson McCullers novel, with Alan Arkin as a sensitive deaf mute. At the SYMPHONY I, Huntington at Mass. Ave. (262-8837).

Hot Millions--Peter Ustinov and Maggie Smith are just fine in this gentle suspense-comedy written by Ustinov and Ira Wallach. At the ASTOR, Tremont St. near Boylston (542-5030).

King of Hearts--Phillipe de Broca's color fantasy, bound to bring some joy into your world. Alan Bates is in it, and the whole thing is blessed with one of the nicest background scores ever, the work of Georges Delerue. At the BRATTLE, beginning Sunday (TR 6-4226).

Lady in Cement--Frank Sinatra in a film that should have been buried in cement. At the CHERI I, Dalton St. in Prudential Center (536-2870).

The Lion in Winter--Pretension unleashed, most notably that of Anthony Harvey, the director, who seems bent on doing everything as conspicuously as he can. Neither Peter O'Toole nor Katharine Hepburn gives much of a performance in this cumbersomely filmed version of James Goldman's play, which was unconvincing to start with. At the PARIS CINEMA, 841 Boylston (267-8181).

Negatives--A ponderous and pretentious excursion into illusion-reality land, starring three ugly people, one of whom was much better in "Marat-Sade" and featuring a soundtrack consisting almost entirely of ominous clicking, gratuitous' screaming, and much too much crumpling of polyethelyne. This way madness lies. At the CHARLES CINEMA, 195 Cambridge St. (227-2832).

A Night at the Opera--George Kaufman and Morrie Ryskind loaded the screenplay with more jokes and comic situations than any movie has a right to have. Groucho, Harpo and Chico are fine and have great foils in Margaret Dumont, Sig Rumann, and the drippy romantic leads, Kitty Carlisle and Allan Jones. Very likely the funniest movie ever made. At the SYMPHONY II, Huntington at Mass. Ave. (262-8837).

Persona--Ingmar Bergman's horror film about split identity. Through Saturday at the BRATTLE (TR 6-4266).

Raisin in the Sun--Lorraine Hansberry's fine drama about being black in Chicago brought to the screen. ClaudiaMcNeil is stunning, and Sidney Poitier isn't half bad. At 2DIVINITY AVENUE, tonight.