As a speech-language pathologist there is no clear cut answer to your question. There are many different types of dysfluencies. For example: Repetition of words (I I I want), phrases (I want I want a drink.), or sounds (D-D-Don't r-r-rock it); Hesitations (pauses in speech or blocks); prolongations (stretching the sounds out--"Mmmmy sissster Jooodi"). Stuttering severity and need for intervention depends on the frequency, duration and type of dysfluency. There are many young "normal" children who "stutter". Some stop without intervention, others don't and become "stutterers". If there is a family history of stuttering, you may want to have your son evaluated by a professional. You should certainly seek professional help if you feel it is interfering with your son's socialization, development and/or education. An assessment by a speech-language pathologist is not going to hurt your son. Isn't it better to be safe than sorry? For more info, you may want to check out the American Speech-Language-Hearing Association.