There is evidence that most detrainment from tropical convection occurs below ∼14 km, about 2 km below the tropopause. On the other hand, it is also generally accepted that convection does occasionally reach the altitude of the tropopause. The question is whether the relatively infrequent penetrations above 14 km are sufficient to influence the composition of the atmosphere above 14 km. Using O₃ and CO data as tracers of convective activity, I quantify the height distribution of mass detraining from convection near the tropopause using data obtained in February 1996. The calculation suggests significant detrainment is occurring as high as ∼380 K potential temperature (∼17 km), with as much as 60% of the mass crossing the 380 K surface detraining above 370 K (∼15 km). These findings contrast with the previously published suggestion that convective transport of mass does not significantly influence the composition of the atmosphere above 14 km.