The objectives were to investigate relationships among concentrations of nitric oxide (NO), estradiol 17 beta (E2), and progesterone (P4) in follicular fluids (FF), and quality of cumulus oocyte complexes (COCs) with respect to perifollicular blood flow (FBF). In Experiment I. follicles (138) were classified according to the presence or absence of FBF (assessed with transvaginal Doppler ultrasonography) and diameter of follicles (small, 2-4 mm; medium, 5-8 mm; and large, >= 9 mm). Concentrations of NO in FF did not differ significantly among these size categories. However, NO concentrations in FF with FBF (54.4 +/- 7.4 mu mol/l) were higher (P < 0.05) than in those without FBF (36.6 +/- 4.1 mu mol/l). There was a positive correlation (r = 0.30, P < 0.05) between NO concentrations and the E2:P4 in FF. Rate of E2 active (E2:P4 >= 1) follicles were numerically 1.2(0.8-1.8) times higher in follicles with FBF (38.1%) compared to those without FBF (25.0%). Moreover, rates of E2 active follicles were 6.1 (0.7-55.2) and 1.3 (0.1-17.3) times higher (P < 0.06) in large (43.3%) and medium (14.3%) compared to small follicles (11.1%), respectively. In Experiment II, quality of COCs from 2 to 8 mm follicles, obtained by transvaginal ovum pick up (OPU), was investigated with respect to FBF. Odds ratio to obtain higher quality COCs from follicles with FBF (47.1%) was 3.3 (1.1-9.6) fold higher (P < 0.05) compared to those from follicles without FBF (14.6%). In conclusion, E2:P4, and NO concentrations in FF, as well as FBF, could be used to determine the functionality of ovarian follicles in cows. Moreover, determination of FBF could be useful to predict quality of COCs in cattle. (C) 2012 Elsevier B.V. All rights reserved.