This paper focuses on the professional development of early childhood teachers in mathematics and science, examining the challenges posed by the increasing need for early childhood teachers, especially for children from culturally and linguistically different backgrounds. The paper discusses the current status of professional development for early childhood teachers and points out the variation in quantity and quality of field experiences for early childhood teachers and the limited focus on mathematics and science in professional development. The paper next presents standards for professional development of the early childhood teacher with reference to mathematics and science, synthesized from the National Science Education Standards, Professional Standards for Teaching Mathematics, and the Professional Standards for Early Education, to: (1) develop good dispositions toward mathematics and science; (2) experience good teaching in mathematics and science; (3) focus on learning about children and the mathematics and science content of specific interest to them; (4) participate in a variety of professional development opportunities situated in a learning community; (5) demonstrate an ability to implement integrative curriculum; and (6) utilize appropriate strategies to establish family partnerships. The paper then describes four professional development programs in Texas focusing on early childhood mathematics and science instruction, specifically trainer of trainer modules, study groups with math and science emphases, a graduate class for early childhood teachers on young children's reasoning and thinking and appropriate math and science, and the Collaborative Coaching Project. (Contains 12 references.) (KB)