What Scheme are you running this with? I tried your code in DrScheme, and it prints "Hello, World!" exactly once, with no error, no infinite loop. I'm not sur

What Scheme are you running this with? I tried your code in DrScheme, and it prints "Hello, World!" exactly once, with no error, no infinite loop. I'm not sure why, but I expect it has something to do with the semantics of "begin" (maybe a bug in DrScheme?); you can make the code work in DrScheme as you describe if you use "let" instead of "begin": (let ((cont #f)) (set! cont (call/cc (lambda (k) k))) (print "Hello, world!") (cont #f)) You can get an infinite loop by changing where the variable is set: (let ((cont #f)) (call/cc (lambda (k) (set! cont k))) (print "Hello, world!") (cont #f))