Most kids start losing baby teeth when they are 5 or 6 years old. The first tooth to fall out is generally the lower front tooth followed by the upper front tooth. The adult teeth then start coming in. Usually, the back adult teeth (6-year-old molars) come in around the same time as the lower front teeth. I do warn parents though that these are not hard rules and every child develops differently. As a rule of thumb, most girls lose teeth before boys do. I have had 4-year-old girls lose their front teeth while I've had 9-year-old boys not lose a tooth yet. In both extremes, there is no need to worry as long as all the adult teeth are present. If the adult teeth are not present, then I recommend that an orthodontist evaluate the child to look at the need for braces.