Numerous studies have demonstrated that the phytohormone abscisic acid (ABA) plays an important role in many processes during seed development. Abscisic acid prevents precocious germination of the developing seed and regulates the expression of specific genes during development. The availability of maize (Zea mays L.) viviparous mutants, which are defective in ABA synthesis or responsiveness to this phytohormone, allowed the investigation of varying physiological ABA levels on expression patterns of specific ABA-responsive genes. The present work indicated that the expression of several ABA-responsive genes is variable among the different viviparous mutants. Among the genes examined, Em showed the highest correlation between endogenous ABA content and transcript levels. Results from ABA studies strongly support the positive role of this phytohormone in inducing Globulin (Glb1 and Glb2) gene expression in maize embryos. In the absence of ABA, no Glb1 transcripts are detected within 24 h of embryo germination. On the other hand, induction of Glb1 is observed in germinating embryos within 18 h in the presence of ABA. Although Glb1 is positively induced by ABA, the endogenous ABA levels obtained from sibling normal and viviparous mutant embryos do not correspond to the increase in Globulin expression in these mutants. Neither Glb1, Glb2, nor Em transcripts are detected in vp1 mutant embryos suggesting that a functional Vp1 gene product is required for Globulin and Em gene expression. These studies indicate that Globulin gene expression in maize embryos is under the control of different factors which require at least a combination of specific endogenous ABA levels and the presence of a functional Vp1 gene product.