The conjecture of Fisher and Hartwig, published in 1968, describes the
asymptotic expansion of Toeplitz determinants with singular generatin
g functions. For more than twenty years progress was made in extending
the validity of the conjecture, but recent computer experiments led t
o counterexamples that show the limits of the original conjecture and
pointed the way to a revised conjecture. This paper describes the hist
ory of the problem, several numerical examples, and the revised conjec
ture.