The purpose of this study is to assess the teratogenic potential of the test article, API-81-15, based upon its ability to inhibit HEPM cell growth. HEPM cell growth inhibition assay is shown to complement the Mouse Ovarian Tumor (MOT) cell attachment inhibition assay in predicting teratogenicity of environmental agents. The test article, API-81-15, was tested in the human embryonic palatal mesenchyme (HEPM) cell growth inhibition assay in the absence of metabolic activation. Exponentially growing HEPM cells were plated at a density of approximately 3.5 x 10(sup 4) cells/35 mm dishes and were incubated at 37+1(sup o)C in a humidified atmosphere of 5% CO2 in air for 23 + or - 2 hours. Three dishes are counted to estimate the number of cells on each dish to establish the background cell count. Following the attachment period, the remaining of the cells were exposed in triplicate to test article concentrations of 500, 250, 125, 62.5, 31.3, 15.6, 7.8 and 3.9 ug/ml for 72 + or - 2 hours at 37 + or - 1(sup o)C. After the treatment period, all media were aspirated, the cells washed with PBS, trypsinized and counted. The data are analyzed to determine the cell number per dish, the average cell number for each test article concentration, and the percent growth in each test article concentration relative to that observed in the solvent control. The ID50 for the first routine assay was 73.2 ug/ml. The average ID50 for the second routine assay was 60.5 ug/ml. The average ID50 (66.9 ug/ml) corresponds to a rating of 3 (table 1). Under the conditions of the assay described in this report, API-81-15 was considered as a suspect teratogen (rating of 3) in the HEPM cell growth inhibition assay without activation.