Wright’s (1969) widely used "unconditional" procedure
for Rasch sample-free item calibration is
biased. A correction factor which makes the bias
negligible is identified and demonstrated. Since this
procedure, in spite of its superiority over "conditional"
procedures, is nevertheless slow at calibrating
60 or more items, a simple approximation
which produces comparable estimates in a few
seconds is developed. Since no procedure works on
data containing persons or items with infinite parameter
estimates, an editing algorithm for preparing
item response data for calibration is appended.