Caracterization of the FAR-IR emission of QSOs is an important goal of ISO in order to derive their dust content, the origin of dust heating and the possible presence of strong starbursts comparable to those of ultraluminous IR galaxies. We propose here a dedicated study of two subclasses of quasars with signposts of high dust content and/or starbursts: strong optical FeII emitters and Broad Absorption Lines (BAL) QSOs. Since there is a correlation between strong FeII and FAR-IR emissions in low redshift QSOs and IR galaxies, one possible explanation of strong FeII emission is supernovae remnants associated with strong starbursts. The broad absorption lines of BAL QSOs could be formed in the gas accelerated through radiation pressure and dust after a starburst. We will also include a few QSOs with "associated" absorption systems of narrow lines at the redshift of the QSOs, since they could be in an evolutionnary stage related to BALs. Our sample includes both QSOs with z 1-2 and of moderate z (0.1-0.4) for comparison. ISOPHOT should detect them in the FAR-IR, even at high redshift if their FAR-IR luminosity compares to that of IR ultraluminous galaxies, and will thus provide the FOR-IR luminosity, dust mass and temperature. CII and OI fine structure lines are among the best tracers of the large amount of warm and dense neutral gas caracterictic of violent starbursts. We propose to search them in the few members of our sample with continuum fluxes strong enough (detected by IRAS) and in a few other strong IR QSOs for comparison.