The present paper describes the effect of heterosis found in a full diallel design 4×4 pure strains of laying hens. There were 36 individually measured hens per combination. In economic terms and with regard to a low food conversion ratio (FCR), positive heterosis was found for egg weight, egg number and total egg mass, while negative heterosis was found for food consumption in the rearing period 0-16 weeks, body weight, weight gain and yolk percentage. On average, there was negative but non-significant heterosis for FCR. Five of the combinations had positive but non-significant heterosis in FCR, while seven combinations had negative heterosis; three were significantly different from zero. No significant differences in mortality between the pure strains and the hybrids were found.