Four new species of free living nematodes are described from the southern part of the Caspian Sea. Oxystomina caspica sp. n. differs from similar species 0. elongata, 0. affinis,
0. pulchella and 0. orientalis by the body length, form of spicula and tail. Halalaimus minusculus sp. n. resembles H. gracilis and H. amphidellus but differs from them in the size of body and cephalic setae and form of spicula. Microlaimus naidinae sp. n. resembles very much M. citrus but its spiculae bear no velum. Sabatieria triuialis sp. n. differs from the closely related S. quadripapillata and S. breuiseta in the number of preanal papillae, form of amphid and body size.