What are the chances of a master's student in computer science from a reputable school getting into MIT or Stanford for a computer science PhD without prior research experience?

I would say that your MS is more of a hinderance than a help here. Look at yourself as someone with a disadvantage -- the admissions committee is looking for a narrative, a story of someone who is so passionate about research, it is their destiny. They did research in high school. Hell they probably were doing research as a small child. In undergrad, they did tons of research. So, naturally they finished undergrad and now it's time for their MS/PhD.But -- whoops -- you decided to get this terminal master's thing. Oops.I'm not saying to give up but I'm saying that, reading applications, this is an orange flag. Of course, everyone understands the born-to-do-research narrative is not true and everyone is an individual. People understand that sometimes you have to wriggle around a bit to find the right path. There is a respect for those that are willing to re-route. This is all good stuff that you can work with. However, I would, sitting on this committee, be gunshy... thinking that... well, how does this person know that research is really there thing?So -- show that research is your thing. Publish a paper. Or do paper-level research, but don't publish it. Take time off and use the stellar hourly rate you can pull as a consultant with that MS degree from a top-10 CS school to fund this work. This makes me forget about your terminal master's (which, btw, is highly stigmatized.... courses are for people who don't know how to teach themselves...) and suddenly see someone who: Has high CS ability (evidence: got good grades at a tough CS school) Cares about research (evidence: you self-funded academic-level research) Is good at research (evidence: you either published research or have paper-level research) My instinct is that, without #2 and #3, your chances are low. Item #2 is remarkable and rare and will make for a great essay that could tip scales in your favor. Without them, it may not hurt to apply -- high-level grad school admissions are highly volatile and you may get lucky -- however you should have a plan in place to apply again the next year with some more research experience under your belt. I can't speak much for other schools but at Caltech, a student from a top CS school with a super-high GPA just wasn't that impressive. But someone from just about anywhere with killer research would get an interview.

3.8 is a fine GPA. But the fact that you have no research experience in your master years is a big hindrance. Remember people who got in to the big four, CMU Standord, Berkeley and MIT in general have both stellar GPA and research experience. Some people even publish at top conference as first author in their undergrad. But the most important thing is your recommendation letter. Without someone who can attest your research potential, your chances even at top 20 schools are slim. Take a look at the resume of those who got in and you will have a more concret sense.

I also think it's most likely 0. The people who you are competing against are likely 4.0s AND have research experience. Without prior research experience you wouldn't have much chance (just yet). Why not take some time off to actually do some research? That will improve your odds. (Hint: Do a masters thesis if you can.)