The influence of mixing maize seed Iots of different harvest years on seed physiological quality and field performance were examined. Two hybrids, AG 303 and C-511 A, and the variety IAPAR 26 were subjected to the following treatments: 100% seeds of preceding year production; 100% seeds of current year production and compound seed lots of preceding and current production years with the respective proportions: 5% + 95%; 10% + 90%; 15% + 85%; and also 10% of dead seeds + 90% of current production year seeds. Physiological quality was measured by germination test, first counting test, accelerated ageing, cold test with soil and field emergence rate. Field performance was evaluated by yield (kg/ha), ear/plot, initial and find plant population (plants/m), stem breakage (%) and lodging (%), with experiments conducted in five locations: Londrina, Ponta Grossa, Irati, Pato Branco and Cambará, in Paraná State. From the results obtained, ín two years (1989/90 and 1990/91), it is possible to conclude that aIthough decreased seed vigour associated with the increased in utilization of preceding year harvest seeds in the mixtures, the treatments tested did not interfere with field performance.