Viking orbiter images are used to study the distribution and morphology of 59 lava flows in the Elysium Planitia region of Mars. Average widths for these flows range from 3 to 16 km, and many of the flows exceed 100 km in length. The aspect ratio (flow length to average width) is highly variable (>40:1 to 294 km from the summit of Elysium Mons. An unusual attribute of five flows is their segmented nature, with up to 13 individual segments on a single flow, which each have a surface area from 25 to 250 km2. Photoclinometry is used to derive an average thickness of 40--60 m for these flows, indicating that individual flow volumes range from 17.7 to 68.1 km3. Plausible values for the effusion rate (101-104 m3 s-1) suggest that individual eruptions could have lasted for a few months to several decades and could have injected between 1.36 and 2.04¿1012 kg of water vapor into the atmosphere, assuming a 1 wt % water content for the parental magma. A total volume for all 59 flows is estimated to be 817--1226 km3, which would have released ~2.04--3.01¿1013 kg of water vapor into the atmosphere or ~0.2% of the amount previously calculated <Plescia, 1993> as the amount released from the Cerberus flows in SE Elysium Planitia. ¿ 1998 American Geophysical Union