To examine the difference between early-onset (< age 3) childhood disintegrative disorder (CDD) and autistic disorder with speech loss (ADSL), 8 children with early-onset CDD (mean age = 7.6 years, SD = 3.8; 6 males) were compared with 92 age and gender-ratio comparable children with ADSL (mean age = 6.8 years, SD = 4.1; 70 males) on 24 variables not directly related to the key features of CDD (regression after normal development for at least the first 2 years after birth). Compared with the ADSL group, the early-onset CDD group had a tendency to have a higher rate of a psychosocial event before speech loss (SL) (early-onset CDD, 75.0% vs ADSL, 37.0%, p = 0.057; effect size (phi) = 0.211, p < 0.05); a significantly higher rate of fearfulness during SL (62.5% vs 4.3%, p = 0.000; phi = 0.551, p < 0.05); and a tendency to have a higher rate of epilepsy (25.0% vs 3.3%, p = 0.050; phi = 0.271, p < 0.05), a tendency to have a lower rate of the Childhood Autism Rating Scale-Tokyo Version (CARS-TV) total score ≥ 30 (75.0% vs 95.7%, p = 0.072; phi = 0.236, p < 0.05), and a significantly lower rate of CARS-TV item 2 (imitation) score ≥ 2 (50.0% vs 82.6%, p = 0.049; phi = 0.221, p < 0.05) on the first visit. The two groups did not exhibit any significant difference in the other 19 variables. The findings of no significant difference in the great majority and a significant difference in the small minority of the 24 variables between the two groups support integrating CDD into regressive autism spectrum disorder and studying CDD as its prototypical form.