An analysis was made of the uncertainty in the prediction of dose to an individual’s thyroid due to the transport of radioactive molecular iodine, 131I2, from air through the pasture-cow-milk pathway. This analysis was facilitated by the adoption of a model consisting of a multiplication of several factors represented by lognormal distributions of values. Results indicate there is a 64, 50, or 23% chance of the annual dose to an individual’s thyroid not exceeding the mean, median, or most probable doses, respectively. However, these results are tentative as a result of the limited amount of data available for annual average dose assessments. The suggestion is made that consideration be given to adopting a probabilistic approach to determining an acceptable probability of an individual receiving a dose that exceeds a limiting value.