Phoenix's domestic-partner registry opens on Monday for couples wishing to make their relationships at least somewhat official.

The registry opens at 9 a.m. Monday at Phoenix City Hall. Registration will take place in Assembly Room B throughout the week before moving to the city clerk's office on the 15th floor.

The registry grants the right to visitation with a domestic partner in any health-care facility in Phoenix. The registration also could be used to demonstrate a domestic partnership to employers or others that offer benefits to employees.

Registry supporters argued that it was necessary because domestic partners have been prevented from dealing with loved ones' medical emergencies by patients' families.

"This policy really will strengthen all families, including gay and lesbian families," Sam Holdren, spokesman for the gay-rights group Equality Arizona, told the city council at the time of the vote.

Barbara McCullough-Jones, executive director of Equality Arizona, said she does not know what to expect with the registry.

"Some want to wait, and others are very excited and eager to get registered," she said.

Couples will be charged $50 to register.

Both parties must appear together to register and must provide a valid photo ID issued by a government agency within the U.S. that includes name, date of birth, weight, height and hair and eye color.

Both same-sex and opposite-sex couples may apply. Both partners must share a residence in Phoenix, be in a committed relationship and share responsibility for each other's common welfare. Neither person may be married to a third person or be part of another domestic partnership or civil union. Each person must be 18 or older, and may not be blood relatives.

McCullough-Jones said she has heard that as many or more opposite-sex couples will register than gay couples.