The ability to understand the meaning of words and sentences is an important determinant of the language development, which also indicates the development of the ability to learn. Bearing this in mind, the research was aimed at studying the level of semantic development of younger primary school-age children. Semantic development was studied from the aspect of understanding the meaning of words and their use in the following lexical relations: homonyms, antonyms, synonyms and metonyms. The research was conducted in three Belgrade primary schools during the school year 2013/2014. The sample was convenient and included 431 second- and third-grade pupils. The Semantic test (by S. Vladisavljevic) was used in the study. Research results showed that none of the pupils had provided the correct answer to all administered tasks. The best scores were achieved on the part of the test referring to antonyms, while the pupils were least successful on the tasks referring to metonyms. Additionally, third-grade pupils were more successful than younger participants, while there were no differences according to gender. The results indicated that it was necessary to devote more attention to different lexical and semantic exercises at preschool and early school age, considering the link between semantic development, the acquisition of reading and writing skills and the (un)successful mastering of the school curriculum in the majority of subjects. [Projekat Ministarstva nauke Republike Srbije, br. 179034: Od podsticanja inicijative, saradnje, stvaralaštva u obrazovanju do novih uloga i identiteta u društvu i br. 47008: Unapređivanje kvaliteta i dostupnosti obrazovanja u procesima modernizacije Srbije]