A novel technique for concentrating ecotoxicants in aqueous and gaseous media using an in-needle microtrap with subsequent gas chromatographic determination was developed. The technique comprises two steps: (1) enrichment effected by passing a liquid or gaseous sample subjected to analysis through a trap of a pew type, a needle with an in-tube fixed sorbent bed, and (2) rapid thermal desorption of pollutants concentrated in the needle microtrap, which occurs immediately in the evaporator of a gas chromatograph. The technique allows impurities to be determined at the concentration level of 1-5 mug/l (liquid media) and similar to0.5 mg/m(3) (gaseous media), with the reproducibility of results estimated at the relative standard deviation of less than or equal to0.1. Prospects of using the method in liquid chromatography and other analytical techniques are discussed. Examples of using the needle microtrap in determining trace aromatic hydrocarbons in aqueous and gaseous samples are given.