To assess the potential use of testate amoebae as biomonitors of atmospheric pollution we studied the relationship between atmospheric nitrogen dioxide (NO2) pollution and testate amoebae density, diversity, and community structure (Protista: Rhizopoda) in (zone 1) and around (zone 2) the city of Besançon, France. NO2 concentrations were on average significantly lower in the city zone (mean: 34.8 ± 9.5 µg/m3) than in the periphery zone (mean: 14.6 ± 4.7 µg/m3). The density of living amoebae was correlated with that of empty tests (0.001