Recent near-infrared imaging surveys have revealed that young pre-main sequence intermediate mass stars (1< M < 8 Msun), such as the Herbig Ae/Be stars are often accompanied with a dense population of partially embedded low-luminosity objects. These young groups, still embedded within their molecular clouds, have not yet undergone significant stellar or dynamical evolution and thus provide unique opportunities to answer some of the fundamental questions concerning the star formation process: 1) What is the origin of the Initial Mass Function ?, 2) What are the timescales for the infall and accretion phases and their corresponding rates ? and 3) how do environmental conditions affect the star formation process ? Deep optical and near-infrared imaging surveys have proven useful in identifying these embedded populations and studying IMF's and frequencies of accretion disk candidates. Further investigating infall and accretion properties of these embedded populations require however observations at longer wavelengths. The mid-infrared domain is particularly crucial to discriminate between different types of circumstellar environments: sources still embedded within residual infalling envelopes (Class I, rising mid-IR Spectral Energy Distributions), opaque circumstellar disks (Class II, slowly decreasing SEDs) and optically thin circumstellar material (Class III, reddened blackbody). We propose a mid-infrared imaging survey with ISOCAM of these clusters in order to fully sample the Class I and Class II populations. This will enable us to: (1) determine the timescales associated with the infall phase, (2) better determine accretion disk statistics (distribution of slopes, frequencies), (4) investigate different environmental conditions and (5) test current disk and infall models. ISOCAM offers the unique combination of high sensitivity and good angular resolution necessary to conduct this program.