Visualization of probe DNA molecules, which exist in a printed dot on an insulating substrate, has been realized by TOF-SIMS. Reproducible PO2- ions derived from the DNAs have been collected from an area of 300 mum x 300 mum by optimizing the measurement conditions. The primary Ga+ ions with a dosage of 2 x 10(12) ions/cm(2) gave approximately 1.4 x 10(4) counts as PO2- for one printed dot in which the numbers of the DNA molecules and the PO, units were calculated as 2.4 x 10(7) and 9.6 x 10(8), respectively. These numbers gave 1.5 x 10(-5) as the secondary ion yield for PO2-. The role of TOF-SIMS in life science industry was also discussed. (C) 2004 Elsevier B.V. All rights reserved.