A total of 65 operators involved in lichen mapping studies in central and northwestern Italy underwent quality control tests during five lichen biomonitoring workshops organized between 1999 and 2000. The results showed that 75% quantitative accuracy and 90% quantitative precision can be regarded as satisfactory levels for lichen biodiversity data; 65% proved to be sufficient for accuracy of taxonomic identification in the field. Average correct assignment of the interpretative naturality/alteration class was only 48.7%. The results indicated the need for taxonomic training.