What are the corresponding titles for "Dr." (in the sense of MD and PhD) in Chinese? The prefix Dr. in English refers to both medical doctors, and PhD graduates. What are the correct titles for these in Chinese? I believe that 医生 is correct to use as a title for a medical doctor, but I don't know if it can be used for a PhD.
All the information is taken straight from Wiktionary's English entries and the Chinese/Mandarin translations thereof. You don't really need to know any Chinese to find the information:

Doctor (physician): 医生, 大夫.
Doctor (person with a doctorate): 博士
Doctor (vet): 兽医

Doctor of Philosophy: 哲学博士 

Graduate (from a university): 毕业生


博士 can be used as a title. For example you'd call me 焦博士 if I was an academic doctor (I wish). 

毕业生 is usually used without a name attached; however, if you have to use it as a title (which is really unusual in either English or Chinese), then you can append the name of the person at the end of it: 毕业生James or 毕业生小焦.