We have demonstrated that the tissue differentiation patterns along the dorsoventral and anteroposterior axes can be controlled by a combination of activin A, concanavalin A (Con A), and retinoic acid. Xenopus blastula animal caps, normally fated to form epidermal tissues, differentiated into ventral mesoderm tissues such as coelomic epithelium and blood-like cells following treatment with activin A (0.5 ng/ml). Dorsal mesoderm tissues like muscle and notochord, were induced by graded addition of Con A. Conversely, Con A (1 mg/ml) induced anterior neural tissues, forebrain accompanied by eyes and cement glands, in the animal caps. Posterior neural tissues, hindbrain with ear vesicles and spinal cord, were induced by graded addition of activin A. Retinoic acid was also capable of shifting the Con A-induced anterior neural tissues to more posterior tissue phenotypes, however, its caudalizing activity was slightly different from that of activin A. These results suggest that the concentration gradients of these three factors can regulate the differentiation patterns along the embryonic axes. The present study provides a suitable test system for analyzing the establishment of the fundamental body plan in early vertebrate development.