A wide variety of tests are available to assess the central nervous system (CNS) function of the toddler and preschool-aged child. These tests vary as to function; qualities and abilities tapped; facility with which they can be learned, administered, and scored; availability of test materials and manuals or training videos; and strength of standardization and validation data. Some were developed to screen development of large numbers of children. Others were developed to evaluate a child for diagnosis of disability or delineation of a child's strengths and weaknesses. Some broadly screen or assess multiple aspects of development, while some focus on specific abilities. A limitation of all these tests is that they tap only a small portion of a child's abilities at a given point in time. Administration of a variety of different tests provides a more complete evaluation of a child's abilities. Tests that can follow a child's development over time tap into the continuum of human development. The ability to measure various aspects of CNS functional development is a first step in addressing our greatest challenge, how to promote and support a child's development.