The NAD kinase (EC 2.7.1.23) from Triatoma infestans has been purified and a specific antiserum against it prepared. Immunochemical techniques have shown that the increase in the levels of NAD kinase in nymphs of T. infestans is accompanied by an increase in the amount of enzyme protein. The enzyme is labeled after injection of14C-labeled leucine in both induced and non-induced insects, but labeling is greater in the former, which further supports the concept that a de novo synthesis of enzyme protein occurs during induction by DDT. The enzyme is heterogeneous by DEAE-cellulose and DEAE-Sephadex column chromatography, but the antiserum does not distinguish this heterogeneity. NAD kinase induction may correspond to a protective mechanism of the insects by increasing the availability of coenzymes required for DDT detoxication.