The purpose of this study is to examine the long-term safety and tolerability of ezetimibe (SCH 58235) 10 mg once daily or placebo in combination with atorvastatin (10 to 80 mg/day) for up to 12 consecutive months in participants with primary hypercholesterolemia.

This study is a long-term extension study of the protocol P00692 parent study.

Inclusion Criteria:

• Has successfully completed the 12-week double-blind, efficacy and safety parent study (P00692).
• If female, has a negative pregnancy test prior to study entry and, if of childbearing potential, agrees to practice an effective barrier method of birth control for the duration of the study and for 30 days after the last statin dose.
• If postmenopausal female receiving hormone therapy, a stable estrogen (ERT), estrogen/progestin (HRT) or raloxifene regimen must be maintained during the study period.
• Is willing to continue to follow their prescribed National Cholesterol Education Program (NCEP) Step 1 diet for the duration of the study.

Exclusion Criteria:

• Has discontinued from the parent study (P00692) prior to study completion.
• Is in a situation, or has any condition which, in the opinion of the investigator may interfere with optimal participation.
• Is a pregnant or lactating female.
• Is human immunodeficiency virus (HIV) positive.