  Recent ISO-data has allowed for the first time observationally based
estimates for source confusion in mid-infrared surveys. We use the
extragalactic source counts from ISOCAM in conjunction with K-band counts to
predict the confusion due to galaxies in deep mid-IR observations. We
specifically concentrate on the near-future Space Infrared Telescope Facility
(SIRTF) mission, and calculate expected confusion for the Infrared Array Camera
(IRAC) onboard SIRTF. A defining scientific goal of the IRAC instrument will be
the study of high redshift galaxies using a deep, confusion limited wide field
survey at 3-10 microns. A deep survey can reach 3 $\mu$Jy sources with
reasonable confidence in the shorter wavelength IRAC bands. Truly confusion
limited images at 8 microns will be difficult to obtain due to practical time
constraints, unless infrared galaxies exhibit very strong evolution beyond the
deepest current observations. We find L^star galaxies to be detectable to
z=3-3.5 at 8 microns, which is slightly more pessimistic than found by Simpson
& Eisenhardt (1999).
