This is a drug-drug interaction study to compare the pharmacokinetics of a 2 mg oral dose of midazolam in adult healthy women of non-childbearing potential when administered alone and when administered along with 8 daily 125 mg doses of PD-0332991. Volunteers will be randomized to one of two sequences. Volunteers in sequence 1 will receive midazolam alone in treatment period 1, followed by multiple dose PD-0332991 and midazolam in treatment period 2. Volunteers randomized to sequence 2 will receive multiple dose PD-0332991 and midazolam in treatment period 1, and following a washout period of no less than 14 days they will receive midazolam alone in treatment period 2.

Inclusion Criteria:

• Healthy females of non-child bearing potential between the ages of 18 and 65 years old.
• A Body Mass Index (BMI) of 17.5 to 32.0 kg/m2 and a total body weight >50 kg (110 lbs).
• A signed informed consent document.

Exclusion Criteria:

• Any evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurologic, or allergic disease.
• A positive urine drug screen.
• Pregnant or nursing females.
• Treatment with an investigational drug within 30 days or 5 half-lives of the first dose of study medication.