We determined the genome size of the Brazilian sciarid flies Bradysia hygida, Rhynchosciara americana and Trichosia pubescens (Diptera: Sciaridae) using absorbance measurements of Feulgen-stained nuclei belonging to these species (and chicken erythrocytes as a standard) to calculate the amount of DNA in picograms (pg) and the number of base pairs (bp), or C-value, for each of these species. The C-values were: 3 x 10(8) bp (0.31 pg) for B. hygida; 3.6 x 10(8) bp (0.37 pg) for R. americana; and 1 x 10(9) bp (1.03 pg) for T. pubescens. The sciarids investigated in this work had considerably higher C-values than the average for previously described dipteran species, including D. melanogaster.