The local chapter of the global human-rights group holds its 27th annual letter-writing drive Monday.

The three-hour Pittsburgh write-a-thon takes place, as usual, at Shadyside’s Calvary Episcopal Church.

At the event, volunteers are supplied with information about human-rights abuses around the world (including the U.S.), from unjust laws to individual cases of imprisonment or persecution of activists. Writers address the letters to the appropriate government officials.

The letters make a difference, says Amnesty. Last year, for instance, one case was that of Jean-Claude Roger Mbede, who was imprisoned for homosexuality in Cameroon. Mbede has since been freed.

Others similarly freed included an Azerbaijani blogger jailed for posting on Facebook a journalist sentenced to hard labor for criticizing the Sri Lankan government.

The write-a-thon usually draws a nice crowd and is a good time to commune with rights-minded folks. There are also, typically, tasty snacks and beverages.

The write-a-thon runs from 6-9 p.m. Mon., Dec. 10. Calvary church is at 315 Shady Ave.