  We present a study of the evolved stellar populations in the dwarf spheroidal
galaxy Fornax based on JHK imaging photometry. The observations cover an
18.5x18.5 arcmin central area with a mosaic of NTT/SOFI images. Our data sample
all the red giant branch for the whole area. Deeeper observations reaching the
red clump of helium-burning stars have also been obtained for a 4.5 x 4.5
arcmin region. Near-infrared photometry led to measurements of the distance to
Fornax based on the K-band location of the RGB tip and the red clump. Once
corrected for the mean age of the stellar populations in the galaxy, the
derived distance modulus is 20.74 corresponding to a distance of 141 Kpc, in
good agreement with estimates from optical data. By taking age effects into
account, we have derived a distribution function of global metallicity [M/H]
from optical-infrared colors of individual stars. Our photometric Metallicity
Distribution Function covers the range -2.0<[M/H]<-0.6, with a main peak at
[M/H]~-0.9 and a long tail of metal-poor stars, and less metal-rich stars than
derived by recent spectroscopy. If metallicities from CaII triplet lines are
correct, this result confirms a scenario of enhanced metal enrichment in the
last 1-4 Gyr.
