Inventories of vertebrate and flowering plants are frequently used as surrogates for estimates of total biodiversity. This is in part because the inclusion of invertebrates and nonflowering plants is perceived as being too time‐consuming, costly, and difficult because of the shortage of specialists. Estimates of the species richness of field samples of spiders, ants, polychaetes, and mosses made by a biodiversity technician and by specialist taxonomists were compared. The biodiversity technician received a few hours training in the taxonomy of each group and separated specimens into recognizable taxonomic units (RTUs). The specialists sorted to species. For the three animal groups the biodiversity technician recorded 165 taxa and the specialists 147, with the error for the ants and spiders being 13% or less. A small amount of splitting and lumping of species was detected. The concordance of estimates remained very similar when small subsamples were used. The procedure was repeated by 13 undergraduates using a subsample of spiders. Their average error was 14.4%. The greatest similarity in estimates was for the mosses, but with high levels of splitting and lumping this result was entirely fortuitous. The results suggest that RTU estimates made by biodiversity technicians may be sufficiently close to formal taxonomic estimates of species richness to be useful for the rapid assessment of biodiversity. They also show, however, that the procedures outlined here should be used on invertebrate and nonflowering plant groups before they can be confidently included in biodiversity surveys.