Katy Perry and John Mayer back together?

U.S. recording artists Katy Perry and John Mayer appear to be giving romance another try after breaking up twice, their friends told UsMagazine.com.

The former couple have dated off and on since last summer, confirming their second breakup in March.

However, Mayer was a guest at Perry's Memorial Day barbecue in Hollywood Hills, the magazine said.

"They seem to be back together -- or back together-ish," one source said. "They were very flirty and having a really good time together. They have good chemistry."

"They were definitely friendly," a second insider said.