Due to large obscuration, the outflow activity of the youngest low-mass
 stars remains poorly understood. Recent ground-based near-infrared
 imaging of outflows from embedded YSOs has opened a promising obser-
 -vational approach using H2 lines which trace radiative shocks. These
 new observations suggest that the fast, highly collimated CO outflows
 emanating from the youngest (Class 0) protostars are driven by jets
 fairly similar to the optical jets observed around some unobscured
 pre-main sequence stars. A unified model is now emerging, according to
 which all CO outflows represent ambient gas that has been entrained
 by an underlying fast jet. However, most low-mass embedded YSOs have
 much weaker CO outflow activity than Class 0 protostars, and we lack a
 direct confirmation of the existence of the jet in these cases.
 ISOCAM provides a unique opportunity to image with a good resolution
 and sensitivity some of the major cooling lines of low-velocity
 radiative shocks. We thus propose to use ISOCAM to extend the ground-
 based to extend the ground-based investigations of the 2.2 micron H2
 line to mid-IR H2 lines of lower excitation levels which will probe
 lower velocity shocks and will be much less sensitive to extinction
 from the ambient cloud. The target fields we have selected have all
 been observed by us with the VLA in the radio continuum, and are
 covered by the central programme survey for YSOs (Nordh et al.).
 By combining all these observations, we hope to reach statistically
 significant conclusions about the nature and frequency of occurrence
 of jets in young stellar populations.