The AIDS Healthcare Foundation in conjunction with Faithful Central Bible Church put on the event from 6 a.m. to 4 p.m. Sunday.
Some 70 certified technicians performed the rapid tests.
"We're using two different kinds of tests. One is an oral swab, and one takes a little finger stick of blood. You just come in, give your sample. Wait 10, 15, 20 minutes, and we call you back in and give you your results," said Whitney Engeran of the Aids Healthcare Foundation.
Officials say there are as many as 15,000 people in L.A. County who are HIV positive but don't know their status because they've never been tested.