Dusty debris around solar-type stars: Temporal disk evolution

Using ISO-ISOPHOT, we carried out a survey of almost 150 stars to search fo r evidence of emission from dust orbiting young main-sequence stars, both i n clusters and isolated systems. Over half of the detections are new exampl es of dusty stellar systems and demonstrate that such dust can be detected around numerous stars older than a few times 10(6) yr. Fluxes at 60 and eit her 90 or 100 mum for the new excess sources together with improved fluxes for a number of IRAS-identified sources are presented. Analysis of the exce ss luminosity relative to the stellar photosphere shows a systematic declin e of this excess with stellar age consistent with a power-law index of -2.