It has been twenty years since the introduction of killer whales to public display. Learning about the biology and behavior of these animals has been a major focus for public educational display, and the result has been the recognition and implementation of programs for successful maintenance and propagation. This talk will center on the demographics of the killer whales in U. S. and Canadian parks-numbers, years in captivity, age, structure of the group based on comparison of length/growth curves and survivorship analysis. Of special interest is the information gained from regular measurement of changes in length over years. The curve for growth rate in the killer whale is linear for several years and then abruptly flattens as growth rate slows. The growth curve for females flattens prior to that of the male. Using these data, it is possible to estimate the age of a whale at first handling and to predict the number of years to maturity.