This study estimated the incidence of speech delay based on a demographically representative sub-sample of 1,328 monolingual English-speaking 6-year-old children. Among six major findings were: (1) the prevalence of speech delay was 3.8 percent; (2) speech delay was 1.5 times more prevalent in boys than girls; and (3) comorbidity of speech delay and language impairment was 1.3 percent. (Author/DB)