The purpose of this study is the teratogenic potential of test article, API-81-15, based upon its ability to inhibit mouse ovarian tumor (MOT) cell attachment to Concanavalin A-coated disks. The MOT cell attachment assay is shown to correctly assign 79% of the 102 tested agents into teratogenic or non-teratogenic categories. This assay may be of value in the teratogenicity assessment of environmental agents. The test article, API-81-15, was tested in the MOT cell attachment assay at dose levels of 100, 50, 25, 6.3, 3.1, 1.6 and 0.8 ug/ml using ((sup 3)H)-thymidine labeled MOT cells. Following the treatment period, the cells were allowed to sediment onto either Con A-coated or BSA-coated disks. The number of cells that were attached to the disks was quantitated by scintillation counting. The ID50 of the first routine assay was 80.7 ug/ml. The ID50 of the second routine assay was > 100 ug/ml. The ID50 of the third assay was 117 ug/ml. The estimated average ID50 (> 100 ug/ml) corresponds to a rating of 3. Under the conditions of the assay described in this report, API-81-15 was considered as a suspect teratogen (rating of 3) in the MOT cell attachment assay.