A survey for filarial parasites was carried out on dogs in Lebanon. The peripheral blood was examined for microfilariae and the skins and carcasses for adult worms. Three methods were used for blood examination: (a) thick blood films stained with Giemsa; (b) a modified Knott's technique (Methylene Blue stained); (c) sodium citrate technique. Two species of filarial worm were found, Dipetalonema reconditum and another species of Dipetalonema which will be described in a later paper. The morphology of microfilariae and adults of D. reconditum is described. The microfilariae of D. reconditum showed a nocturnal sub-periodicity. Attempts were made to find vectors by feeding Aedes aegypti, Aedes phoeniciae, Culex pipiens molestus and Clenocephalides felis on an infected dog. Developing and infective stages were recovered only from C. felis.