Graybill is charged with multiple counts of practicing medicine without a certificate, identity theft and sexual battery by fraud. He's being held on $590,000 bail and is due back in court on Oct. 16.
The Los Angeles Police Department says Graybill used advertisements on Craigslist to solicit potential clients by offering them up to $4,000 monthly for sperm donations in support of stem cell and other research.
Police say two men showed up to donate and he conducted exams and sexually fondled them. The physical examinations allegedly took place in Marina Del Rey and Santa Monica. Authorities say Graybill didn't have an actual clinic.
Police say there are a total of 24 victims, but so far only two have come forward.
If you have any information about the case, you're asked to call the Los Angeles Police Department Operations West Bureau's Sexual Assault Detail at (213) 473-0404 or 1-877-LAPD-24-7.