This study compared 48 hyperactive children with 49 age-and-sex-matched controls. Significantly more hyperactive children had auditory, visual, language, reading, and learning difficulties, and the birth weight of hyperactive children was significantly lower than that of controls (3,058 and 3,410 g, respectively; p less than 0.01). In addition, significantly more hyperactive children had frequent coughs and colds, polydypsia, polyuria, and a serious illness or accident in the past year than controls, but there was no increase in asthma, eczema, or other allergies. Serum essential fatty acid (EFA) levels were measured in 44 hyperactive subjects and 45 controls. The levels of docasahexaenoic, dihomogammalinolenic, and arachidonic acids were significantly lower in hyperactive children than controls (docosahexaenoic: 41.6 and 49.5 micrograms/ml serum respectively, p = 0.045; dihomogammolinolenic: 34.9 and 41.3 micrograms/ml serum, p = 0.007; arachidonic: 127.1 and 147.0 micrograms/ml serum, p = 0.027). These findings have possible therapeutic and diagnostic implications, but further research is needed to attempt to replicate these differences.