The stabbing was reported at 2:38 a.m. in the 400 block of Ellis Street.
An argument between two groups of people outside a pizza parlor turned physical when a suspect took out a knife and cut a 37-year-old man in the throat and slashed a 28-year-old man in the face, San Francisco police spokesman Officer Albie Esparza said.
The pair was taken to San Francisco General Hospital. The 37-year-old man was in serious but stable condition while the 28-year-old is expected to survive, Esparza said.
A third victim suffered contusions in the altercation but did not require hospitalization, Esparza said.
The group of suspects fled after the stabbing and had not been found as of this morning, according to Esparza.
He said one suspect was described as a black man in his 20s who wore a silver baseball hat, a black jacket with gray sleeves, blue jeans, a long chain necklace and had a chinstrap-style goatee.
A second suspect was described as a black man in his 20s who wore a red football jersey, blue jeans and had shoulder-length dreadlocks, Esparza said.
A third suspect was described as a black man in his 30s who is tall, has a skinny build and wore a green camouflage shirt, blue jeans and possibly a black baseball cap, according to Esparza.
Anyone with information about the stabbing is asked to call the Police Department's anonymous tip line at (415) 575-4444 or to send a tip by text message to TIP411 with "SFPD" in the message.