The purpose of this research focused on the developmental aspects of avian (chick) embryonic tissue during the axial phase upon exposure to various concentrations of positive photoresist JSR KFR M20G. Specific development of neutral tube closure, heart defects, cephalic formation, and axial defects were studied. Methodology was derived from the modified New vitelline membrane system. Concentrations of JSR KFR M20G used were 0.0006%, 0.0003%, and 0.00015%. Resulting from exposure at these concentrations, abnormalities consistent with cephalic (forebrain, midbrain and hindbrain) lack of development, neural tube closure defects (referred to as Spina Bifida in humans and mammals), failure of axial development, and arrested development (death) were seen. This particular methodology lends itself to studying teratogenic effects of substances on embryos at very early stages of development (before gastrulation and beyond) in which standard reproductive toxicity testing using inhalation techniques can miss. Occupational exposure of substances to human embryos at similar early stages could result in spontaneous abortions or resorption before a pregnancy is even suspected or could have numerous teratogenic, mutagenic, and embryolethal results. This type of chick embryo model system can also be used in determination of specific gene interruption in relation to tissue/cell damage resulting form a particular chemical exposure. The results form this research are preliminary and warrant further investigation at earlier developmental stages in the avian embryo model system.