The major Ca²⁺ entry pathway in electrically nonexcitable cells is store-operated, in which the emptying of intracellular Ca²⁺ stores activates Ca²⁺ influx [1, 2]. We have identified the olf186-F gene which encodes the Orai protein as a component of the store-operated Ca²⁺-channel in the plasma membrane of the secretory cells of Drosophila melanogaster larval salivary glands[3]. The main aim of these investigations was to study the mechanisms underlying the activation of store-operated Ca²⁺-entry in these organs. For this purpose, we used Drosophila strain that expresses genetically encoded Ca²⁺-sensor G-CaMP1.6 in larval salivary glands. Salivary glands were dissected under the HEPES-buffered physiological saline solution. The passive depletion of intracellular Ca²⁺-stores was promoted by applying of 10 μM ionomycin and/or 10μM thapsigargin. Ca²⁺-related variations of G-CaMP1.6 fluorescence were studied using a confocal microscopy. To determine whether thapsigargin mobilizes Ca²⁺ from intracellular stores, secretory cells were perfused with EGTA-containing medium and then exposed to 10 μM thapsigargin. Resting G-CaMP1.6 fluorescence intensity in single secretory cells was 33.21 ± 2.33 conventional units (n = 51) in 0-Ca²⁺ medium. The addition of thapsigargin caused a non-transient increase in the G-CaMP1.6 fluorescence intensity in all cells observed (n = 51, mean = 44.44 ± 3.64 c.u., P ≤ 0.05). The re-admission of external 2 mM Ca²⁺ resulted in a significant elevation of the G-CaMP1.6 fluorescence intensity (n = 51, mean = 85.97 ± 10.29 c.u., P ≤ 0.001). Additionally, there was some variability among cells in the rate of rise of the G-CaMP1.6 fluorescence intensity and the magnitude of the peak achieved. Ca²⁺ ionophores, e.g. ionomycin, can also be used to promote the passive depletion of intracellular Ca²⁺ stores, although they also directly transport Ca²⁺ across the plasma membrane [4]. Drosophila salivary glands treatment by ionomycin (10 μM) in Ca²⁺-free medium caused a non-transient increase in the G-CaMP1.6 fluorescence intensity by 11 % (n = 30, P ≤ 0.01). After the re-admission of 2 mM Ca²⁺ all secretory cells (n = 30) exhibited synchronous Ca²⁺ transients and the G-CaMP1.6 fluorescence intensity elevated by 89 % (n = 30, P ≤ 0.001). This could result from Ca²⁺ entering into the cells under the Ca²⁺/H⁺-exchange and/or the store-operated Ca²⁺-entry activation upon the emptying of the intracellular store. Therefore, thapsigargin mobilizes Ca²⁺ from intracellular storage sites and inhibits its uptake by the endoplasmic reticulum Ca²⁺ stores. The activation of the store-operated Ca²⁺ entry across the plasma membrane after depletion of Ca²⁺ stores could suggest about its role in the maintenance of Ca²⁺ homeostasis in the secretory cells of Drosophila melanogaster larval salivary glands.