In the first four years of ALD newborn screening, from 16 February 2016 through 15 February 2020, California screened 1,854,631 newborns for ALD and other peroxisomal disorders (Figure 1), including 945,344 males, 900,917 females, and 8370 infants with no biological sex reported; 77,637, or 4.2% had elevated C26 at the first tier and went onto the second tier of screening; 355 or 0.5% were screen positive on the second tier of screening and had ABCD1 gene sequencing performed before they were referred to a metabolic clinic for a diagnostic workup. Here, ABCD1 is linked to X-linked adrenoleukodystrophy.