The present invention relates generally to the methods for the treatment and diagnosis of conditions mediated by IL-5 and excess eosinophil production, and more specifically to mAbs, Fabs, chimeric and humanized antibodies. More particularly, methods are provided for reducing eosinophils in a human in need thereof, which method comprises administering to said human a composition comprising at least one anti-IL-5 antibody, wherein at least one anti-IL-5 antibody provides a mean maximum plasma concentration of said anti-IL-5 antibody of at least about 1.03 ± 0.21 µg/mL, an Area Under the Curve value of at least about 15.5 ± 2.7 µg/day/mL and a serum half-life of about 16.2 ± 2.1 days to about 21.7 ± 2.8 days.
