Four commercially available medicinal aerosol products in India have been assessed for the aerosol size distribution at two different humidities using a ten stage cascade impactor device having a quartz crystal microbalance system. An indigenously made nebulizer in use in a city hospital has also been assessed for its aerosol efficiency. The size range is between 0.05 and 25 mu m. Mode in the aerosol mass size distribution is between 0.4 and 1.6 mu m at 30% relative humidity (RH) and between 0.4 and 3.2 mu m at 85% RH for three inhalers: the mode for powder inhaler is between 3.2 and 6.4 mu m at 30% RH and 25 mu m at 85% RH. The mode for indiginous nebulizer is between 0.05 and 0.1 mu m. These results are discussed in the context of the deposition of aerosols in the human respiratory system.