This is a study to assess the safety, efficacy, and tolerability of MK0859 in patients with primary hypercholesterolemia (large amounts of cholesterol in the blood) or mixed hyperlipidemia (high levels of LDL cholesterol, triglycerides, and low levels of HDL cholesterol in blood) This is an early phase trial and some specific protocol information is in progress and not publicly available at this time. (Full information is available to trial participants).

Inclusion Criteria:

• Patient is between 18 and 75 years of age
• Patient can be on a stable diet for the study
• Patient has a stable weight for more then 6 weeks before the study and has not participated in a weight loss program

Exclusion Criteria:

• Patient has chronic heart failure or a history of heart disease
• Patient has blood, digestive, or central nervous system disorders
• Patient is pregnant or nursing
• Patient is HIV positive