This paper presents the results of a study of local vortices, and dust devils, on Mars as observed by Viking Landers 1 and 2. It is found that these vortices are most common during Martial spring and summer, as occurs on earth. Seven of the vortices wind speeds that may raise dust from the Martian surface. There is no indication that these possible dust devils contribute to the planet-wide spread of major dust storm. However, it appears that they may help in maintaining the atmospheric dust content. The data indicate that there is no preference in rotation direction, at least to core diameters to 300 m (corresponding to a region of influence of about 3 km diameter).