The Montana Department of Health and Human Services administers the state's registry for patients and caregivers. Those who are registered are allowed under state and local law to possess certain amounts of marijuana.

The state health department's website includes:
Answers to Frequently Asked Questions
Application form for patients/caregivers (downloadable, printable)
Physician recommendation form (downloadable, printable)
Forms for renewing registrations (patients/caregivers must renew annually)

The health department's website can be found here:
http://www.dphhs.mt.gov/medicalmarijuana/