A substantial body of research suggesting the possibility of biochemical, physiological and psychological effects of air ionization is reviewed. Two experiments testing certain of these claims were conducted. The first study examined the influence of negative ions on alpha activity in the EEG and simple reaction times. The second experiment tested the relationship between reported weather-sensitivity, susceptibility to migraine, and changes in the performance of simple, two- and four-choice reaction time tasks with exposure to negativeions. No significant effects attributable to exposure to negative ions were found in either experiment. The implications of these null results are discussed.