Using five different protocols, two enzymes, nicotinamide adenine dinucleotide phosphate phosphohydrolase (beta-NADPHase) and sodium trimetaphosphatase (TMPase), were localized in the acinar cell of rat pancreas by ultrastructural cytochemistry. The beta-NADPHase cytochemical localization was realized at pH 4.8 and pH 3.9. At pH 4.8, the beta-NADPHase activity was found in the Golgi intermediate saccules, lysosomes, gland lumen, and tubular structures, described as snake-like tubules (Beaudoin AR, Grondin G, Lord A: Eur J Cell Biol 33:275, 1984; Beaudoin AR, Grondin G, Lord A, Pelletier M: In Proc 42nd Ann Meeting Electron Microscopy Soc Am. San Francisco Press, CA, 1984). There was no detectable beta-NADPHase activity at pH 3.9. The TMPase cytochemistry was done at pH 3.9 according to Oliver (J Histochem Cytochem 28:78, 1980) and at pH 3.9 and 4.8 with the medium described by Berg (J Histochem Cytochem 8:92, 1960). TMPase localization varied according to the protocols. It was found in tubular structures described as "basal lysosomes," lysosomes, and zymogen granules, whereas Golgi saccules were generally negative. Our observations showed that the structures identified as "basal elongated lysosomes" and revealed by TMPase (Oliver C: J Histochem Cytochem 28:78, 1980; J Histochem Cytochem 31:1209, 1983) were morphologically similar to snake-like tubules (SLT) revealed by beta-NADPHase. Relationships between SLT and mitochondria as well as lysosomes and plasma membranes were observed. Using amylase-specific antibodies, it was also shown, by the protein A-gold immunocytochemical technique, that SLT do not contain amylase and, in fasting conditions, would not be involved in the transport of secretory proteins.