The classic investigations of the malaria epidemics in the Punjab led to the conclusion that in this most populous and most malarious province of the present-day Pakistan, epidemics occurred regularly at intervals of approximately eight years. Against this background, the results of a Malaria Control Programme launched in 1975 are examined. The Programme, supported by USAID and WHO, represents in economic terms the greatest effort made against malaria in the country. Malathion, the main attack weapon of the Programme, was used on an unprecedented scale. This created logistic and--unexpectedly--toxicity problems among the spraying workers. Despite these difficulties, an over-all reduction of 76% in the slide positivity rate was observed in the first two years of operations of the Programme. The authors warn against measures which may curtail the activities of the Programme when, according to the cyclical periodicity of malaria in the Punjab, an epidemic wave can be expected in 1980-81, with inevitable repercussions all over the country.