How probable is it to get an std from giving oral sex?

Good!: If your partner has a disease, the chances are quite good. Sex is not a game. Serious business with significant health and psychological consequences!

The probability : Depends on if the other person is infected (which you usually have no way of knowing beforehand). Oral sex has potential to transmit a number of sti's. Herpes simplex, hiv, hpv, gonorrhea, chlamydia, syphilis ; hepatitis can be spread via oral sex.