Social calls of Pipistrellus nathusii were repeatedly recorded in South Bohemia during years 1999-2005. Recorded social calls belong to males (regular sedentary display, songflight), females and juveniles (maternity colonies) or unknown individuals (behavioural situations in the mating season, advertising calls during emerging from maternity roost). Mating calls are composed from three main parts (ABC) as a rule; the fourth part (D) can be attached. The most often recorded motives were ABC, ABCD, ABCB(BBB)D, ABC(BCBC)D, AB, AD, BC and long D-sequencies interrupted by B or several short steep FM signals. Particular males were determined by individual traits of advertising calls (especially the lowest frequency of the third call of V-shaped signals (part C), the lowest frequency of FM call (part B) and the number of component in regular sedentary display). Calls of one male were analyzed in detail (difference in number of components, frequency and duration of particular components and parts). The fourth part (D) of advertising calls of males produced more in the peak of mating season and in sedentary display, contains signals similar to calls recorded in maternity colonies with spectrogram shapes copying letters L, M, N, I, U, V, W. Distribution and frequency characteristic of particular types are individual and several gradual transitions were noted from the fourth part (D) to the first part (A) of advertising call. Some males emitted long sequences of these signals during sedentary display interrupted by the second (B), the second ant the third part (BC) or by steep FM signals falling down from 70 to 20 kHz with duration 0,6 - 4 ms and interval 5-26 ms. In maternity colonies was often recorded also double-note communication and gradual transitions from short FM signals during emerging similar to the first part (A) of advertising calls of males and occasionally structure A and ABC.