In the article, the subject of the analysis was Latvian-Lithuanian-Polish dictionary for farmers (Lotewsko-litewsko-polski slownik praktyczny dla rolników i robotników rolnych), printed in Riga in 1937 . This dictionary had been designed as a support for Polish seasonal agricultural workers, tens of thousands of which entered Latvia and had to communicate with Latvian farmers, officials and local people.The problem of dictionary's author is not yet solved. However, it appeared to be proved that the Polish part of the Dictionary represents a cultural dialect of the local Polish language which had been largely under influence of Eastern Slavic language (Russian and/or Belarussian). The influence of Latvian language is obvious, too. From about 1500 analysed words more than 300 peculiar cases were found, among them 53 types of graphical peculiarity.First of all it was lack of letter i used as a palatalization sign (12 cases), hesitation in the usage of the 'softened ' letters akin to 'z' and 'c', application of letter 'i' instead of 'y' or 'j', unhyphened spelling of the 'nie' with verbs, and so on. Types of found phonetic and syntactic peculiarity were respectively 55 and 49, most of them were known and described by other investigators. At inflexion level 79 peculiarity types were found, most numerous of which were addressing forms using 'wy'. Almost one third of all peculiarity types were lexical ones (86), 23.26% of them were semantic innovations, and further 31.40% were disused and old words and meanings. Loans from Russian amount to 4.65%, while from Latvian to less than 3.5%. Further investigations on the Polish language in Latvia will enable to compare this regional dialect with other regional Polish dialects outside borders of the Polish state.