Abstract:In this paper, I introduce the longitudinal method in general, and more specifically, the method applied in a two-decade-long language shift research project conducted in a Romanian-Hungarian bilingual village, Kétegyháza (hereinafter LongBiLing: longitudinal study on bilingualism). I will primarily present the language choice changes occurring in the first decade (1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)) but I will also give a short review of the findings comparing the two decades. The aim of the project is to find out at what stage the Romanian-Hungarian language shift process is in the Hamers and Blanc's (1989) unidimensional model of language shift and to what extent the process can be considered gradual (Mesthrie 2001). In a previous article I sought to find out in which bilingual national minority (out of the six) in Hungary sustainable bilingualism was the strongest (Borbély 2015). In this paper, I discuss language use domains (25 language choice situations) in a local community of Hungary's Romanian national minority investigated with a longitudinal method. The aim was to learn about the differences among the linguistic domains in order to find out in which domain bilingualism was the most sustainable.