We present the results of the five mid-IR 15 \mu m ( 12-18 \mu m LW3 band ) ISOCAM Guaranteed Time Extragalactic Surveys performed in the regions of the Lockman Hole and Marano Field .
The roughly 1000 sources detected , 600 of which have a flux above the 80 % completeness limit , guarantee a very high statistical significance for the integral and differential source counts from 0.1 mJy up to \sim 5 mJy .
By adding the ISOCAM surveys of the HDF-North and South ( plus flanking fields ) and the lensing cluster A2390 at low fluxes and IRAS at high fluxes , we cover four decades in flux from 50 \mu Jy to \sim 0.3 Jy .
The slope of the differential counts is very steep ( \alpha = -3.0 ) in the flux range 0.4-4 mJy , hence much above the Euclidean expectation of \alpha = -2.5 .
When compared with no-evolution models based on IRAS , our counts show a factor \sim 10 excess at 400 \mu Jy , and a fast convergence , with \alpha = -1.6 at lower fluxes .