• INCLUSION/EXCLUSION CRITERIA:

Screening Visit:

Inclusion:

• Parents agree to use a multivitamin with minerals if their child is selected to continue to the cholesterol supplementation clinical trial.
• Parents agree to not change the doses of other dietary supplement throughout the clinical trial, including megavitamins.
• Male or female between the ages of 4.0-12.0 years at the time of consent/assent.
• Clinically diagnosed with an ASD for which no cause has been detected.
• Anticonvulsants used for the treatment of a seizure disorder will be permitted if the dosage has been stable for 3 months, and the subject is seizure free for at least 3 months.

Exclusion:

• Known pregnancy.
• Subject has SLOS or known cholesterol synthesis/regulation disorder.
• The subject has had an anticonvulsant dose change in the preceding 3 months or a seizure in the preceding 3 months.
• DSM-IV diagnosis of Rett Disorder, childhood disintegrative disorder, schizophrenia, another psychotic disorder, or substance abuse.
• A significant medical condition such as heart disease, hypertension, liver or renal failure, pulmonary disease, diabetes, or unstable seizure disorder identified by history, physical examination, or laboratory tests.
• Dietary supplementation doses, including megavitamins, have changed within the preceding 3 months.
• Currently on or has taken a statin medication within the preceding 3 months.
• Currently on or has taken dietary cholesterol supplementation within the preceding 3 months.
• Subjects will be excluded if they are on other medications or supplements that affect cholesterol or other lipid levels.
• Subjects with gastronomy feeding tubes (G-tubes) will be excluded.
• Subjects for whom English is not the primary language will be excluded.

(No subjects will be excluded based on race, ethnicity or gender).

Characterization Visit:

Inclusion:

• Same inclusion criteria as the Screening Visit.
• Participants must have a mental age of 18 months as measured at the Characterization Visit by the age-appropriate form of the Stanford Binet-V, the Differential Abilities Scale, or the Mullen Scales of Early Learning (N.B. potential subjects who test below 18 months of age, but are otherwise eligible, may be admitted to the study following a case review convened by the Multisite Steering Committee).
• Child must have an ASD diagnosis using DSM-IV and clinical judgment in order to proceed to the other components of the Characterization Visit.
• Neuroleptics will be permitted for the ASD+Hypo group only if the dosage remains stable for the duration of the study.
• Neuroleptic medication free for at least three months (ASD+Hyper and ASD+Normal only).

Exclusion:

• Same exclusion criteria as the Screening Visit.
• Allergy to lanolin or soy (Hypo+ASD only).
• Non-verbal mental age below 18 months as measured by the developmentally-appropriate form of the Stanford-Binet-V, Differential Abilities Scale, or the Mullen Scales of Early Learning (N.B. potential subjects who test below 18 months of age, but are otherwise eligible, may be admitted to the study following a case review convened by the Multisite Steering Committee).
• Did not meet the criteria for an ASD during the Characterization Visit.

Double-Blind, Placebo-Controlled trial phase for ASD+Hypo Only:

Inclusion:

• Met Characterization Visit inclusion criteria and completed Characterization Visit procedures.
• Met criteria for hypocholesterolemia in ASD.

Exclusion:

-Same exclusion criteria as the Characterization Visit.

Open-Label Trial for ASD+Hypo only:

Inclusion:

- Subject continues to meet double-blind, placebo-controlled trial phase inclusion criteria.

Exclusion:

- Subject started a neuroleptic medication or medication that affects cholesterol synthesis or metabolism.

Family Members of ASD+Hypo only:

Inclusion:

- Biological parent(s) and full or half-sibling(s) of any age.

Exclusion:

- Those individuals not willing to provide a blood sample or a saliva sample for DNA.