A cDNA segment encoding the Ca2+-binding protein, parvalbumin, was isolated with the use of antibodies, from a lambda gtll expression library of Xenopus laevis tadpole poly(A)+ RNAs. The bacterially expressed beta-galactosidase-parvalbumin fusion protein of one lambda recombinant shows high affinity 45Ca2+ binding. The sequence of the tadpole parvalbumin is highly similar to previously characterized beta-parvalbumins of other organisms. Data from protein and RNA blotting experiments demonstrate that parvalbumin is absent in oocytes, eggs, and early staged embryos, and only becomes expressed during embryogenesis at the time of myogenesis. The protein can be detected in individual developing muscle cells and in muscle fibers of tadpole tail muscles. A simple method is also described for the isolation of neural tube-notochord-somite complexes from Xenopus embryos.