We have described a reasonably accurate method of predicting ribavirin small-particle aerosol dosage administered by nasal inhalation or endotracheal tube adjusted for age, sex, weight, and fever. Regional distribution of inhaled small particles was also presented according to age. This methodology will predict dosage for many other drugs given in this way as long as they are water-soluble and their density in solution does not differ materially from unity. A standardized method of estimating dosage should make possible quantitative comparisons of treatment in different studies. Also presented were studies in which triple the usual dose of ribavirin aerosol was administered, but in one third of the usual dosage period. Aged patients with chronic obstructive pulmonary disease tolerated the treatment with little difficulty, and a group of infants and children with RSV disease recovered promptly with no evidence of intolerance to the treatment. This modification of dosage offers increased accessibility for patient care, and the therapeutic benefits seem as good as the longer regimen. Higher respiratory secretion concentrations with the high-dose regimen may conceivably improve therapeutic results over current methods.