INDIANAPOLIS (AP) — Some college students in Indiana can use their student IDs to cast ballots in the primary, but others will have to bring a different form of identification to the polls.

Using a student ID would be convenient for young Indiana voters, who have been courted by Democratic presidential hopefuls hoping to win the state's May 6 primary. Yet not all student cards qualify under Indiana's voter ID law.

The law requires voters to show identification issued by the U.S. government or Indiana, which includes the state's public colleges and universities. Identification used for voting must include a person's name, photo and an expiration date.

Indiana University student IDs meet all those requirements and can be used at the polls. The cards are good for five years, and students can renew them if they are in school longer, said spokeswoman Susan Williams.

However, ID cards at Purdue and Ball State universities have no expiration date. Those students will need other ID, such as an Indiana driver's license or U.S. passport, if they want to vote in the primary.

Purdue and Ball State do not include expiration dates in part because they have no way of knowing how long a student will be in school, according to officials.

Ball State considered adding expiration dates to student IDs a few years ago, but the idea never gained traction, said spokesman Kevin Burke. The university had just revamped its cards in 2004 and would have had to pay $30,000 to redo them.

"They didn't want to face that expense," Burke said.

Purdue would have to pay $150,000 to switch to a system that included set expiration dates, said spokeswoman Jeanne Norberg.

Tippecanoe County election officials recently considered finding a way to work with Purdue IDs, which include encoded information that may indirectly act as an expiration date when read with a scanner wired into the university's computer system. Even if the information would qualify under state law, technical issues would be a problem, said Tippecanoe County Clerk Linda Phillips.

So Purdue students will need other forms of ID if they want to vote. Phillips expects many students to cast absentee ballots early since the semester ends before the primary.

College students in Indiana can either vote by mail in their home county or state, or change their permanent residence to the county where their school is located. Changing permanent residence includes getting an Indiana driver's license and vehicle registration for students with cars, according to the Indiana Secretary of State's office.

Young voters in Indiana have been targeted in recent weeks by Democratic presidential candidates Sens. Barack Obama and Hillary Rodham Clinton.

Obama's campaign gave away thousands of tickets for a free Dave Matthews concert, and offered the chance for high school and college students who register new voters to play basketball with the senator. Chelsea Clinton has spoken at several campuses across the state as her mother and Obama vie for Indiana's 72 pledges delegates.

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On the Web:

Voting information for college students:

www.in.gov/sos/elections/hava/college-index.html

Information on Indiana's voter ID law:

www.in.gov/sos/photoid/