We evaluated a new criterion for behavior or reactivity estimation for Saanen dairy goats, based on a ranking of attitude of goats submitted to social isolation from their herd mates. We also evaluated the influence of their behavior on milk production and composition during the whole lactation period and on reproductive characteristics. Twenty-three dairy Saanen goats, aged from 2 to 9 years old, fourteen primiparous and nine multiparous, were divided into two groups according to their reactivity. Nonreactive and reactive animals were allocated in groups one and two, respectively. Milk samples were collected at an interval of 15 days and a ruffian was used to identify the first post-calving estrus. Approximation time showed a mean of 21.42+/-32.70 seconds, which was significantlyrelated to the attitude of the animals. Daily mean of individual milk production was 1.30+/- 0.26 kg, varying from 0.25 to 3.50 kg. Milk yield and composition, besides reproductive attributes, were not significantly affected by reactivity. Reactivity was not affected by parturition. Attitude allowed classification of dairy goats according to their reactivity; however, reactivity did not affect physiological, productive and reproductive attributes of dairy goats.