The research activities in the Zoology research unit basically concern the study of genetical and phenotypical variation of Men. During the past decades, our research activities were mainly focused on problems of human growth and development. Studies of genetic influences on growth and maturation through the analysis of familial and twin data have thrown more light on the impact of heredity and environment on human development. Various studies of environmental influences on growth have been conducted, such as the study of the effect of environmental pollution by lead on growth in childhood, the effect of various socio-economic factors on the development of children during infancy, and the study of the effect of diseases on growth and maturation, such as asthma, hypophosphataemic vitamin-D-resistant rickets, whooping cough, measles. Several studies have been conducted in developing countries, such as West Bengal, Zaire, and Guatemala. A number of growth studies have resulted in the production of population-specific growth references or growth standards: Belgium, Poland, France, West Bengal, etc. These standards allow the verifying of whether the attained body length or body weight of an individual child lies within the range of normal variation, whether the increase in size over one-year intervals is normal, and whether the pattern of growth over a longer period has a shape within the normal range. Finally, the phenomenon of secular trend, i.e. the change in overall size of growing children and adults from one generation to another, has been extensively studied in the Belgian population.