The object of the study was to investigate the effects of seedling age, and different levels of N, K and K/N on quality and yield of tomato grown in perlite bag culture. Seeds of Big Boy F1 sown in perlite and subsequently seedlings were planted in ten-liter PE bag filled with coarse perlite. Four fertigation regimes were applied to the plants concerning four N (103, 110, 113 and 120 mg l -1 ), four K (186, 195, 258 and 275 mg l -1 ) and two K/N (1,6 and 2,5) levels. Thrace element levels were the same for all the fertigation regimes. Seedling were planted at three different growth stages; 1)appearance of first inflorescence (7 week-old), 2)50% flower opening on first truss (8,5 week-old) and 3)fruit set on first truss (10,5 week-old). Although effects of seedling age on total, marketable and early yield, and cracking and blossom-end rot occurrence were not statistically significant, total, marketable and early yield were higher when the seedling were planted at the time of fruit set on first truss. The highest total, early and marketable yields were obtained from the transplants planted at fruit set on first truss with FR1 (plants were fertigated with the high K/N starter solution: K/N= 2,5; 110 mg l-1 N and 275 mg l-1 K until the fruits on the first truss reached 2cm in diameter, then with the low K/N mainfed solution; K/N= 1,6; 120 mg l-1 N and 195 mg l-1 K for the rest of the vegetation).