The Griffiths Mental Development Scales (GMDS) is one of a variety of tests available for assessing the development of young children. It consists of two separate developmental scales, one scale for infants and toddlers (aged 0–2 years) and the other for young children (aged 2–8 years), making it one of the few developmental tests that can be used to assess children from birth across all areas of their development.

The GMDS was developed in the UK in 1954 by Ruth Griffiths, who observed children in their natural environments while they were engaged in their everyday activities. Griffiths's purpose was to develop an instrument that contained a comparative profile of abilities across various domains of development, and which would facilitate early diagnosis of deficits in child development. Although standardised in the UK, the GMDS is widely used throughout the world and is especially popular in South Africa (Luiz, Oelofsen, Stewart & Michell, 1995).

In South Africa, testing and assessment have been heavily criticised as possessing limited value for culturally diverse populations (Foxcroft, 1997; Nzimande, 1995; Sehlapelo & Terre Blanche, 1996). Despite these criticisms, it has also been pointed out that, regardless of its flaws, testing remains more reliable and valid than any of the limited number of alternatives. It is argued that since testing plays a crucial role within assessment internationally, the focus should be on valid and reliable tests for use within multicultural and multilingual societies (Plug in Foxcroft, 1997). Thus, one of the aims of this chapter is to determine the extent to which the GMDS is a valid and reliable measure for assessing the development of South African children.

The original GMDS has been extensively researched and compared to other commonly used developmental tests and shown to be valid (Luiz, Foxcroft & Stewart, 2001). Subsequent to the revision of the GMDS Infant Scales in 1996 and the Extended Scales for older children in 2004, research emerged that assessed the strengths and weaknesses of the revised scales, much of which has been done in South Africa (for example, Laughton et al., 2010b; Luiz, Foxcroft & Povey, 2006). What follows is an overview of this research, preceded by a brief description of the GMDS.