I think by two, they are supposed to put two words together. I think if they are having problems, it's good to catch it early. My friend's son was slow with talking. The first thing the G.P did is send him for a hearing test. That came back fine, but the hospital put them in touch with a speech pathologist who comes to the house and plays with the boy for an hour or so once a week, and they also have some group sessions.