Describing 21 of the HIPAA Security Rule’s 42 implementation specifications. To meet the addressable implementation specifications, a covered entity must (i) assess whether each implementation specification is a reasonable and appropriate safeguard in its environment, when analyzed with reference to the likely contribution to protecting the entity's electronic protected health information; and (ii) as applicable to the entity - (A) Implement the implementation specification if reasonable and appropriate; or (B) if implementing the implementation specification is not reasonable and appropriate—(1) document why it would not be reasonable and appropriate to implement the implementation specification; and (2) implement an equivalent alternative measure if reasonable and appropriate.
NIST SP 800-66 Rev. 1 under Addressable
(45 C.F.R., Sec. 164.306(d)(3))