SCIENTIFIC ABSTRACT We propose to study the 2.5 to 12 micron spectrum of about 80% of the sources in the 46 active galaxies CfA sample with PHOT-S in chopping mode and ISOCAM with LW filters No. 2(5.0-8.5 mu) and No. 7 (8.5-10.7 mu). The remaining sources are either too faint (no IRAS detection at 12 micron) or the subject of a different observing CP program. To the CfA AGN's, we have added a set of about 20 bright Seyfert galaxies. The CAM broad band images are necessary to understand the spatial distribution of the flux and how it may affect the energy distribution observed with PHT-S. The CfA sample is a well controlled and complete hard X-ray selected sample of Seyfert I and Seyfert II galaxies in sbout equal proportions. Hence, the PHOT-S spectra and ISOCAM images will constitute an ideal data-base for statistical studies. Our main scientific goals are the following: (i) disentangle the various emission components - thermal and non-thermal - which contribute to the observed near and mid-IR flux (ii) search for spectral features characteristics of dust (iii) search for broad (>3000 km/s) spectral lines in Seyfert II galaxies which are thought to be obscured Seyfert Is, and (iv) search for molecular bands as tracers of the putative molecular torus which is postulated to surround the core of AGNs. This programme is complementary to that by Rodriguez- Espinosa and collaborators who plan to use PHT-P and PHT-C to study a similar sample . Because the list of AOT is longer than 99, the proposal has been split into two. This is the first part. OBSERVATION SUMMARY All sources are observed both with PHT-S and CAM in single pointing mode. The PHOT AOT used is PHT-40 in chopping mode. With ISOCAM, we use AOT CAM-01 with LW broad band filters No. 2 (5.0-8.5 micron) and No. 7(8.5-10.7 microns) at a pixel magnification of 1.5 arcsec. Exposure times have been computed with the simulators on the basis of the measured IRAS 12 micron flux and under the assumption that the frequency spectral index is -1.2. The background flux used in the computation is that measured by IRAS for all sources which are at least 15 degrees away from the ecliptic plane. For the remaining, ones we multiplied the IRAS-background by 1.5 to be on the safe side. The PHT-S exposure times yield an average signal-to-noise ratio of at least 10 in the continuum over the 2.5 to 12 micron band. For bright sources, the PHT exposure times (and S/N) have been increased to 256 sec so as to be larger then the slewing time. The same CAM exposure times of 100 s is used for all sources, which includes dark current measurements (40 s) and a flat overhead of 20 s. Such a time is sufficient to yield a signal-to-noise ratio of 80 on a 100 mJy point source. The total S/C time is 114,888 s (31.9 hrs) and 115,168 s (32.0 hrs) for the autumn and spring launch, respectively. CONCATENATION: We request the CAM and PHT-S observations to be concatenated for two reasons. First to save slewing time, and second and more important, to avoid problems related to variability. AGN's are known to be variable in the near IR.