The Merck Manual Online

Merck & Co., Inc. is a global research-driven pharmaceutical products company.:
They publish several books, which they offer free on-line.

"Patients & Caregivers
The Merck Manual--Second Home Edition
The world's best-selling home
medical reference
Available online
Available online in other languages

The Merck Manual of Health and Aging
A comprehensive guide to the changes and challenges of aging
Available online

Healthcare Professionals
The Merck Manual of Diagnosis and Therapy
The world's most widely used medical textbook
Available online
Available online in other languages

The Merck Manual of Geriatrics
A comprehensive review of geriatric medicine and care of the elderly
Available online
Available online in other languages

Chemists
The Merck Index
A one-volume encyclopedia of chemicals, drugs and biologicals
Sample content available for free. Complete online version requires subscription.

Veterinarians
The Merck Veterinary Manual
A comprehensive, reliable source of information on all aspects of animal healthcare
Available online"