Based on own collections made in the southern governorates of the Republic of Yemen between 1997 and 2002, 110 new and noteworthy records of vascular plants are provided. Five taxa, Iphigenia oliveri, Kleinia squarrosa, Parthenium hysterophorus, Rhus glutinosa subsp. neoglutinosa and Poskea socotrana are recorded as new for the Arabian Peninsula, and Pistacia aethiopica is confirmed; 23 species are recorded as new and four are confirmed for mainland Yemen; 77 species are recorded as new for the southern governorates of Yemen or larger parts of them. Brief comments are given on the phytogeography of the taxa. Rhus flexicaulis, a species hitherto considered an endemic of SW Arabia, is found conspecific with the widespread African R. vulgaris, and provides, for priority reasons, the correct name for this species; the most recently described R. gallagheri from Oman is also conspecific with it. Justicia areysiana is accepted as the correct name for the S Arabian endemic formerly known as Bentia fruticulosa.