The waiting time distribution for solar flares has been considered. Using G
eostationary Operational Environmental Satellite X-ray data, we show that a
local Poisson hypothesis for solar flares is not consistent with observati
ons, while the observed distribution is well reproduced by a Levy function,
which displays asymptotically a power-law tail. The origin of the observed
waiting time distribution is then attributed to the fact that the physical
process underlying solar flares is statistically self-similar in time and
is characterized by a certain amount of "memory".