The family Tubificidae are characterized as 'small aquatic worms, up to 200 mm in length, with setae in four bundles per segment, with usually an interminate number of setae per bundle.' The family Tubificidae according to present systematic studies contains approximately eighteen genera. Representatives of two of the genera, Limnodrilus and Tubifex are the most commonly found types. Tubificids have a reputation for resistance to pollutants. The common name of 'sludge worms' attest to that. However, no quantitative work on the extent of this resistance has been carried out. For a term such as 'tolerant' to have meaning, some quantification must be carried out under standard laboratory procedures. This report presents some data from such procedures and is an attempt to quantify the tolerance of tubificid worms to three common types of pollutants, the metals, lead and zinc and the wood preservative, sodium pentochlorophenol.