A new biochemical index has been proposed, based on the DNA amount in the larva related to dry weight, to estimate the nutritional condition of marine fish larvae. Starvation induces a strong and fast increase of this index, which can be assessed al the individual level. Weighing very small quantities of dry matter is difficult. It is suggested that carbon content should be used, which can be quantified by accurate standard techniques, Results of a preliminary calibration experiment on sole larvae fed in captivity at three temperatures show a strong correlation between dry weight and carbon. DNA/C values are not the same for the early development stages (symmetrical larva) or the later ones (metamorphosing larva), both levels being quite independent of the rearing temperatures despite great differences in growth rates. DNA/C should provide a convenient and accurate tool for assessing the nutritional condition of field-caught specimens. (C) 1997 International Council for the Exploration of the Sea.