KONGA (AKA: I Was a Teenage Gorilla (USA)) IMDb Page

Also starring Michael Gough, Margo Johns, Jess Conrad, Claire Gordon & Austin Trevor. FILMED IN "SPECTAMATION"!!

Thought to be dead in a plane crash while doing research in Africa, a brilliant botanist/scientist returns home to his teaching post while continuing experiments on his little monkey with the help of his assistant/lover. A breakthrough occurs and the chimpanzee is transformed into a man in a gorilla suit. When our scientist starts falling for a sexy co-ed, the woman he's promised to marry gives Konga an extra dose of stuff and voila, he grows right through the roof of the house and becomes an Attack of a Fifty Foot Man in a Gorilla Suit named Konga. Throw in some very large carniverous plants, some priceless dialogue, surprisingly good acting, lots of cliches and you've got a campy delight

Also see a tongue-in-cheek review here