Chromospheric activity, as seen by the presence of a central K2 emission in the Ca II K λ 393.4 nm line, is studied in F- and G-stars of all luminosity classes. K2 equivalent widths have been measured and corresponding absolute K2 fluxes (power per unit area at the stellar surface) calculated. Large K2 equivalent widths and thus easily detectable chromospheres occur only for stars later than about F8 but the absolute level of K2 flux does not significantly change between F0 and K0; there is no break in chromospheric activity between F- and G-stars. The apparent break, cited in the past (e.g. Wilson, 1973) is illusory and due to the observational threshold being different for different spectral classes.