Each year at these meetings we are presented with estimates of losses due to diseases in cotton. The mean values of these losses over a 30-year period (1952 through 1981) are presented in figure 1. Seedling diseases represent the largest estimated source of losses over this 30-year period; they were the leading source of losses in 13 of those 30 years. The questions I would like to address are: 1) what is the nature of these losses, 2) are we measuring or estimating the real losses, and 3) can these measurements be improved? Although I am dealing primarily with crop loss estimates, many of these evaluations can pertain also to estimates of fungicide efficacy.