The health ministry on Friday revealed a plan to attempt to decode the full genomes of around 90,000 cancer and other patients in about three years.
Patients with deadly cancers will be the first subjects examined.
The ministry hopes research on full genetic information, including DNA, will lead to discoveries on disease mechanisms, treatments and new drugs.
Under the plan, about 64,000 cancer patients and some 28,000 others with intractable diseases will be subjects for the research.
Analysis will also be conducted in advance for some 16,000 lung cancer and ovary cancer patients, and about 5,500 patients with such diseases as muscular dystrophy. Patients with these cancers are rarely expected to survive for five years.
The ministry will research blood, cells and tissues stored in medical institutions and from samples provided by the patients. It will then use the results to draw up a full-fledged research plan covering a greater number of people.