More than two hundreds of citizens are recently suspected to have been exposed to unexpectedly excessive dose of ionizing radiation in the residential environment in Metropolitan Taipei, Taiwan. A much higher risk of radiation-induced neoplasm, hereditary or genetic damage might have been incurred in these victims without appropriate warning. There is urgent need for well-designed and organized medical or public health professionals to provide estimation of biological dosimetry for all these individuals. Several biological markers specific for ionizing radiation exposure have been employed in the previous radiation accidents in several countries. A few newly developed markers are playing more important roles for estimation of chronic low level, low linear- energy-transfer (LET) radiation. A review of these biological dosimetry and monitoring for citizens described is offered, though not comprehensive. This is intended to provide update informations and to frame better direction of medical responses in the coming future.