To understand the safety and efficacy of Revlimid® 5 mg Capsules (hereinafter referred to as Revlimid) in patients with "relapsed or refractory multiple myeloma" (hereinafter referred to as "relapsed or refractory MM") who have received long-term treatment with it under the actual condition of use.

1. Planned registration period This period started on the date of initial marketing of Revlimid and will end at the time when the planned number of patients to be enrolled, 300, is reached (estimated to be approximately 1 year and 3 moths).
2. Planned surveillance period This period started on the date of initial marketing of Revlimid and will end 3 years after the last enrolled patient begins receiving Revlimid (estimated to be approximately 4 years and 3 months).

Inclusion Criteria:

• Relapsed or refractory MM patients in the special use-results surveillance (all-case surveillance) (hereinafter referred to as the all-case surveillance) who have received Revlimid treatment for at least 7 cycles at institutions cooperating in performing the all-case surveillance and this surveillance.

Exclusion Criteria:

N/A

Relapsed or refractory multiple myeloma (MM) patients in the special use-results surveillance (all-case surveillance) (hereinafter referred to as the all-case surveillance) who have received Revlimid treatment for at least 7 cycles at institutions cooperating in performing the all-case surveillance and this surveillance.