Hang on, before you all frighten this person. If your cat otherwise seems healthy, bright eyes, shiny coat, no discharge from eyes or nose or rear end, he should be ok, cats often vomit at will, either through something inedible or just because. That is why they nibble on grass. I have a cat who throws up when he feels like it, its just bad luck, as long as he is eating and drinking fine, dont worry, check he is up to date with his worming programme. Some cats are fussy devils and will throw up at the drop of a hat even when they have just eaten their meal! It could be he is a fast eater and gorges himself too quickly. Try feeding him little and often. RQ x