Background/Objectives: This study examined the development of speech, expressive vocabulary, and receptive vocabulary in boys with Fragile X Syndrome (FXS), with a focus on the contribution of the Fragile X Messenger Ribonucleoprotein (FMRP), while controlling for the effects of nonverbal IQ, maternal education, and Autism status on the development of these skills. Here, FMR1 is linked to fragile X syndrome.