Subjects with a complete paralysis of the abdominal muscles and severe or lesser involvement of the intercostals were studied. The author analysed, under electromyographic control, the flow-volume curves by measuring flow at 50% (V50) and at 25% (V25) of the observed and theoretical vital capacity (CV) above observed residual volume. The results were compared to a group of normal subjects in three situations: sitting and lying in air and sitting in water. A sloping, head down position was also studied. In the handicapped, instantaneous flow at 50% CV was significantly lower than normals in all situations; at 25% CV the difference was not significant but expiration was incomplete for those sitting in air. For the handicapped, sitting in water, the residual volume was close to that of normal subjects sitting in air and the last part of the flow-volume curve was the same gradient as of normal subjects sitting in air: this enabled some comparisons of instantaneous flow. In order that measures of instantaneous flow were made at the same inflation volume, they were made at 50% and 25% of theoretical vital capacity in the handicapped. The results did not differ from those of normal subjects sitting in air. The situation was less satisfactory lying in air, only useable in practice, the most handicapped subjects having notably reduced outputs compared to those whose motor deficit was less severe. The head down position was as for outputs at very low volume.