1. A total of 240 Hy-line brown laying hens (36-week-old), were used in this 8 week experiment to evaluate the effect of caprylic acid and Yucca schidigera extract (CY) on production performance, egg quality, blood characteristics, and excreta microflora. 2. Layers were divided into 5 dietary treatment groups which consisted of: (1) NC, basal diet; (2) PC, basal diet + 110 mg/kg of tylosin; (3) CY1, basal diet + 30 mg/kg caprylic acid + 30 mg/kg Yucca extract; (4) CY2, basal diet + 60 mg/kg caprylic acid + 60 mg/kg Yucca extract; (5) CY3, basal diet + 120 mg/kg caprylic acid + 120 mg/kg Yucca extract. The Yucca extract contained 12·5% saponins. 3. Egg production was unaffected, whereas egg weights and feed efficiency were linearly improved by the addition of CY. There were no differences in the egg quality parameters throughout the experimental period. Plasma total triglyceride and cholesterol concentration in plasma and egg yolk were decreased as utilisation of CY increased. The Escherichia coli counts were linearly inhibited by the CY treatments when compared with the NC treatment at both the 5 and 8 week stages. No difference was observed on the Lactobacillus population through the whole experimental period. 4. In conclusion, the addition of 120 mg/kg caprylic acid and 120 mg/kg Yucca extract exerted positive effects on egg weight and feed efficiency, decreased the serum and yolk cholesterol concentration and reduced the proliferation of Escherichia coli.