A minimum of 20 aquatic, adult Notophthalmus viridescens were captured approximately every other month during 1980 in order to investigate seasonal changes in body size and blood parameters. Hemoglobin concentration, hematocrit, mean cell hemoglobin, sex, weight, snout-to-tail length, snout-to-vent length, and the presence of trypanosomes on blood smears were determined. Environmental variables measured included temperature (range 5–26°C), oxygen concentration (range 5.7–12.2 mg/L), and pH (range 6.5–7.5) of water at the pond's edge. Three anemic specimens (< 0.03 gHb/100 ml blood) were found. The only significant (P < 0.05) seasonal effects were that the mean hematocrit of the July sample was greater than that of the March sample and the incidence of trypanosome infection of the March collected newts was lower than those collected in May, July, and August. Significant (P < 0.01) linear relationships were found within the body size and blood parameters but not between them. Females had significantly (P = 0.000) higher hematocrits than males. The hemoglobin concentration and hematocrit did not correlate with the assumed seasonal oxygen demands of the newt.