A full advertisement call in the tokay gecko (Gekko gecko) is made up of two phases. The first phase consists of 2–3 successive rattles of increasing intensity. The second phase contains a series of 4–11 binotes (mean 6.5), each of which sounds like “gerjai”. All rattles and binotes have the same fundamental frequency of about 100 Hz (90–115Hz). A rattle has a dominant frequency of 835 Hz with almost all energy density below 4 kHz. The first note of each binote contains 11 distinct harmonics with varying dominant frequency. The dominant frequency and harmonics in the second note of the binote gradually vary from the first binote to the last one. Advertisement calls of tokay geckos show diel cycles and seasonal variations. Light and ambient temperature strongly affect the vocal activity in both field and laboratory. The frequency of advertisement vocalization increases in late spring in parallel with the rise of androgen levels and gonadal masses.