The purposes of this study are to determine: - whether standard or higher doses of pemetrexed should be given to patients with ovarian or primary peritoneal cancer that has recurred; - the safety and side effects of standard and higher doses of pemetrexed given to patients with ovarian or primary peritoneal cancer that has recurred; - whether standard or higher doses of pemetrexed can help patients with ovarian or primary peritoneal cancer that has recurred.

Inclusion Criteria:

• Patient must have been diagnosed with ovarian or primary peritoneal cancer
• Patient must have had 1 or 2 prior platinum-based chemotherapeutic regimens.
• Patient must have adequate health status.
• Patient compliance and geographic proximity that allow for adequate follow up is required.
• Signed informed consent from the patient or legal representative is required.

Exclusion Criteria:

• Patient is pregnant or breast-feeding
• Patient has received treatment within the last 30 days with a drug that has not received regulatory approval for any indication at the time of study entry.
• Patient has previously participated in another study investigating pemetrexed.
• Patient is unable or unwilling to take folic acid, vitamin B12 supplementation, and corticosteroids.
• Patient cannot be taking nonsteroidal anti-inflammatory drugs around the time of administration of study drug.