The National Toxicology Program (NTP) was established by the DHHS to coordinate and manage the Department's toxicology programs which develop scientific information necessary to protect the health of the public from exposure to hazardous chemicals. In selected toxicology studies determination of the concentration of test chemical or metabolites in biological samples along with the calculation of basic toxicokinetic information is required to help select dosages, route of administration and vehicle for toxicology and carcinogenicity studies, correlated toxic effects with systemic availability, and ultimately, improve the usefulness of the toxicology study in risk assessment. the majority of the chemistry support work for toxicity/carcinogenicity studies; procurement test substances, identity low level impurities, development and evaluation of formulations for dosing animals, is carried out by large chemistry contractors. A bioanalytical support contractor is especially needed for measurement of analytes other than the substance being studied. Thus, the chemistry support lab may be best for analysis of the test chemical is feed, but the analysis of a metabolite of that chemical in urine may be more economically performed in a laboratory specializing in bioanalytical chemistry. Analysis of substances not directly derived from the test chemical may also be done more economically in a specialty laboratory. Measurement of malatonin in animals exposed to EMF and measurement of biomarkers of oxidative stress and examples.