The practice of making retrograde pyelographic studies with use of radiopaque mediums was first suggested by Von Lichtenberg and Voelcker1 in 1906. Since then many kinds of iodine derivatives have been tried, some of them toxic to the subject, until the use of sodium iodide in 10 to 12% solution was established as being free from danger. The modern type of contrast medium dates from a little more than a decade ago, and each year since then has seen new products presented to the medical profession. Recently, experiments were performed with products containing determined percentages of antibiotics in an attempt to avoid reactions that occur after retrograde pyelography, which sometimes assume serious proportions. But perhaps it would be of greater avail to reconsider basic principles of technique than to rely on covering up the damage with antibiotics. In this regard, we should like to relate some personal observations.