Families of the American hostages and concerned citizens in communities across the country will join beginning today in a variety of special ceremonies to mark the first anniversary of the seizure of the U.s. Embassy in Tehran a year ago Tuesday.

At 5 p.m., just about sunset, a candlelight vigil will be held opposite the Iranian embassy, at 3001 Massachusetts Ave. NW. Several hunmdred people, including a number of Foreign Service officers and their families, are expected to attend.

Similar vigils have been held every Sunday since last Thanksgiving, under the sponsorship of a group of concerned citizens. But this one is expected to draw an especially large crown because of the occasion and heightened speculation that the hostages could be released before the presidentail election, which falls on the same day as the one-year anniversary.

"Our smallest crowd ever was about six people, in a pouring rain last March," said Joseph Keyerleber, an audiovisual writer-producer for the General Accounting Office and former Peace Corps volunteer. The candlelignt vigils were his ideas.

"We had our biggest crowd last Christmas -- 250 or 300," he said, "and then during January and February they fell off to between 20 and 40."

The Washington Cathedral will offer special prayers for the hostages at its three services Tuesday, at 7:30 a.m., noon and 4 p.m. At the latter, the Evensong service, the boys' choir will sing special music.

In Johnstown, Pa., a group that calls itself the Combined Veterans for Sgt. Ragan's Return, will hold a special flag-raising at Sandyvale Cemetery, where they regulary meet. Tonight they will revamp their outdated plans for a grand homecoming for the hostage from their town, Army Master Sgt. Regis Ragan.

"We had our plans all set for a parade, a thanksgiving mass and a reception, but after a year it's hard to tell what we've got left of that," said Charles L. Penatzer, a disabled veteran who is helping to organize the plans.

In a small town near Reading, Pa., the Rev. Richard Schaefer will say a specail prayer during church services, as he always does, for hostage Col. Thomas Schaefer, his brother. Tuesday he will represent his brother's family at special ceremonies planned to honor the hostages on the main campus of Pennsylvania State University, featuring the choir.

"I want to go there to thank people for their concerns over the year," Shaefer said. "It has been a rather awesome experience for us, that expression of warmth. You can just sense their frustration. They say, 'How can we help?' But there's really no answer."