Secretion of proteolytic enzymes by cells has been implicated in tissue remodeling during embryonic development as well as in invasive neoplastic diseases. We studied the regulation of type-IV-collagenase activity in Tera 2 human embryonal carcinoma cells, which in the undifferentiated state proliferate rapidly and are tumorigenic. The undifferentiated cells produced relatively low levels of matrix-metalloproteinase-2 (MMP-2) activity. This activity was not markedly affected by exogenous basic fibroblast growth factor (bFGF) or 12-O-tetradecanoyl-phorbol-13-acetate (TPA), even though the plasminogen activator activity of the cells was increased by these agents. Tera 2 cells can be induced by retinoic acid to differentiate into quiescent cells, of which many express neuronal characteristics. The type-IV-collagenase activity of the cells increased markedly during the differentiation. This increase was mainly due to increased expression of MMP-2. Expression of tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) was not markedly affected by the differentiation of Tera 2 cells. The results show that in the Tera 2 cell system, increased expression of MMP-2 is characteristic of the differentiated derivatives. This is in contrast with many other model systems, where increased type-IV-collagenase activity is associated with the malignant phenotype. This pattern of regulation may reflect the facts that Tera 2 cells resemble early embryonic cells and that their differentiation mimics related cell-differentiation processes in the developing embryo.