One hundred and twenty patients (64 men and 56 women, aged 19 to 63) with chronic pyelonephritis were subdivided into two groups: a control group of 30 subjects and an experimental one of 90 subjects. Experimental subjects underwent short wave therapy (460 MHz, 50-60 W, for 8-20 minutes) in the lumbar area. Lumbosacral pain disappeared in 87 out of 90, subjects, intercostal pain in 20 out of 28, headache mitigated in 40 out of 53, asthenia was markedly reduced in 49 out of 50. Systolic and diastolic hypertension was reduced, as well as the Kakorski-Addis count in urine. Diurnal diuresis and lysozyme increased, while IgG, IgA and IgM were reduced.