High kilovoltage radiography had its beginning with super-voltage technique and is presently accomplished with the 350 KV chest x-ray system. The physical reasons to explain the improved visibility with this technique are: (1) absorption coefficients of bone and soft tissue, (2) more uniform bone visibility, (3) x-ray spectrum, (4) visual responses, and (5) depth resolution. In this study, 350 kV and 120 kV chest x-ray techniques were compared by evaluating 15 parameters. Based on our data and the results of previous large clinical studies, a list of disadvantages and advantages is offered. The entrance dose for an average 350 kV posteroanterior chest radiograph is 8 mR, or about one-third that with 90 kV technique.