The ecological researches on Bombina v. variegata (Linnaeus, 1758) carried out in Lombardy beginning from 1994 are still in progress. Here, attention is focused on the seasonal pattern from 1994 to 2001 and thermal ecology of a population living at 450 m a.s.l.; these data were compared with other Bombina populations present at higher altitudes. The activity cycle of yellow‐bellied toads started in April or May and lasted for 4–5 months. Breeding occurred from the end of May to early August (mean = 60.33 days, SD = 7.03). Females laid eggs on 50 ‐ 71 days, while larval development was completed in 28–107 days (mean = 54.83; SD = 35.12). Yellow‐bellied toads left the aquatic site from August to September, although in 1996 one specimen was captured in November (TH2O ‐ 7.3 °C TAIR = 6.9 °C). During different years (1994–2001), the number of adult specimens captured (NTOT = 673) varied significantly between the two sexes (G = 23.185; df = 7; P = 0.002). Also the analysis of individual annual phases (beginning of activity, reproduction, pre‐hibernation) revealed significant differences in sex‐ratio (G = 14.309; df = 5; P = 0.014). The M/F ratio was 1/1 at the beginning of the season, skewed to males during the breeding season (May‐July), but was in favour of females before hibernation (August‐October). Concerning thermobiology, the beginning of activity started with mean temperatures above 10 °C. Analysis of thermal data showed that the breeding period was not correlated with mean air temperature (Spearman, rs = 0.081; df = 4; P = 0.8), while a weak negative correlation was found between the duration of reproduction and mean water temperature (Spearman, rs = ‐0.531; df = 4; P = 0.1). Water temperatures proved also negatively correlated with the length of larval development (Spearman, rs = ‐0.69; df = 3; P = 0.05).