With a background as a nuclear physicist he is currently an Author, lecturer, active in the UFO research community, and regularly appears in documentaries regarding UFOs.
Back in 1955 Stanton received his BSc. and MSc. Degrees in physics from the University of Chicago. After that he worked as a nuclear physicist for 14 years, employed by several large companies with GM, Aerojet General, GE being a few of them. Stanton claims to have worked on several classified projects involving nuclear powered rockets and space propulsion systems.
His interest in the UFO phenomena started in 1958, and since 1967 he has held many lectures at colleges and professional groups in 50 U.S states, 10 Canadian provinces and in several other countries.
Friedman has written and co-authored many popular books involving UFOs and labels himself as a UFO investigator, author and lecturer.
Here's collection of a few of the titles Stanton has written
It's hard watching UFO documentaries without stumbling over commentaries or appearances, which shows he is very well known and respected in the UFO community. He appeared three times on Larry King in 2007 and 2008 dealing with UFOs.
Here's a few youtube videos featuring Stanton Friedman
Stanton Friedman calls himself the original civilian investigator of the Roswell case, but he is also known for his investigations in the Betty and Barney Hill abduction case, one of the first and most famous abduction cases covered by media.
The testimonies provided by Bob Lazar is mind boggling, but according to Stanton Friedman official web site there's some strong indications that Lazar is simply a fraud.
In general he back up his arguments with facts, but there are questions on some skeptic sites dealing with his interpretation of the facts.Stanton sometimes references to statements made by Betty Hill under hypnosis but it is a fact that memories can be distorted during hypnosis. Therefore I personally think that the testimonies made by Betty Hill while under hypnosis has to be taken under consideration.
Regarding the Roswell case and the possible cover up by the U.S government he has some pretty strong arguments, but arguments are not evidence.
Friedman claims, quote "There is Overwhelming evidence that the earth is being visited by Intelligent controlled extraterrestrial space crafts. There is however no way for a normal person to prove or disprove this claim, either due to classification or lack of said evidence.
Stanton does not personally claim to posses any evidence of Alien visitation on earth, so all we can really do is to consider his arguments either plausible or implausible. There are several skeptic sites dealing with Stanton and I encourage you to read those as well to get your own unbiased opinion.
As with all leading scientists and investigators in the UFO phenomena there are critics and believers, this is normal as long as no part has strong physical evidence to back up their claims or opinions.