When the Federal Bureau of Investigation was founded 75 years ago, few law-enforcement officials thought in terms of ''organized crime'' or checking ''Soviet spying.'' The Soviet Union didn't even exist then. So the few officials who worked for the predecessor to today's super-sophisticated, computer-oriented FBI would hardly recognize the changes that have taken place in national crime-fighting techniques - or the mandate given the bureau this week by President Rea-gan to bolster efforts to combat organized crime and Soviet espionage.
The extent of the change can be measured by the very size of today's FBI headquarters - a structure that occupies one square block of downtown Washington. Inside that building, many developments have occurred in recent years that invite public approval. More women and minorities can be found working for the agency, many of them as agents. There is far less secrecy than was the case under the long tenure of former FBI director J. Edgar Hoover. At the same time the FBI's dedication to remaining at the forefront of scientific and technical breakthroughs in law enforcement methods is as great as ever.
Americans have always been somewhat ambivalent about the FBI - viewing it with a degree of concern while valuing its outstanding crime-fighting work. And perhaps that ambivalence is as it ought to be in a democratic society where the rights of the individual are so important. But, in any case, all Americans can join in applauding the FBI this anniversary week, while recalling how vital it is that the nation's law-enforcement agencies maintain a scrupulous regard for the laws they are asked to protect.