6 severe asthmatic patients were followed for 24 hours using a visual analogue score of dyspnoea and by studying the airway resistance. Their treatment consisted either of two inhalations of placebo or of two inhalations of fenoterol every 5 hours. It appeared that there was only a correlation between the dyspnoea score and respiratory function score for the largest variations of resistance induced by inhalation of sympathicomimetics. The inverse was that altered function offering only small fluctuations was not correlated with a sensation of dyspnoea.