Most often stuttering is identified with a speech disorder or speech disfluency However it resembles a disorder consisting of linguistic, biological psychological and social factors, as well as relations between them The onset of stuttering usually occurs in the preschool age or even earlier, though relatively little concern has been devoted to this period The article presents a review of the latest research on stuttering in preschool age A distinct disproportion between particular elements of stuttering structure have been observed Research concerns manly the linguistic factor and is focused on speech disfluency, while studies on the biological, psychological and social factors are insufficient Research on relations between them is rare Despite efforts of a number of researchers, differential diagnosis of preschool stuttering and natural speech disfluency is still controversial, as is early therapeutic intervention In research it is usually omitted that the essence of speech disfluency is its changeability It continually appears and disappears The causes of this mysterious phenomenon are still unknown