Lettuce (Lactuca sativa L.) is an annual plant of the Asteraceae family, which is grown as a leafy vegetable. Worldwide lettuce is mostly produced on soil. For its development during vegetation, lettuce requires essential macro- and microelements, which uptake by root system. Microelements are present in lettuce in lower content than macroelements, but are essential for its development, as they contribute many physiological processes in the plant. There are many factors which effect content of microelements and one of the most important ones is fertilization. The goal of this research was to determine the effect of fertilization by different phosphorus forms on microelements content in lettuce. The field fertilization experiment was set up in Velika Kosnica (Zagreb County, Croatia) with lettuce cultivar 'Aquarel' according to the Latin square method with three fertilization treatments: T1 (control, without fertilization), T2 (500 kg/ha YaraMila Complex; phosphorus in polyphosphate form) and T3 (370 kg/ha Petrokemija NPK 15-15-15; phosphorus in orthophosphate form). Average lettuce leaves samples were cut up, dried at 105°C and homogenized. The samples were digested by nitric acid (HNO3) and perchloric acid (HClO4) in microwave owen. Iron, zinc, manganese and copper were determined by atomic absorption spectrometry-AAS. Dry matter was determined gravimetrically by drying until constant mass. The highest dry weight (DW) content was determined in T3 treatment (8.85 % DW). Microelements content in dry matter of lettuce leaves (mg/kg dry matter) ranged: Fe 1280-2373, Zn 36.0-48.5, Mn 54.1-87.6 and Cu 9.4-10.7, while in fresh matter (mg/100 g fresh matter) it ranged: Fe 10.5-20.6, Zn 0.30-0.41, Mn 0.45-0.76 and Cu 0.078-0.091. The highest values of microelements were determined in the treatment without fertilization (T1) because potassium, applied in fertilization treatments, probably had an antagonistic effect on their uptake.