Medical radiation from x-rays and nuclear medicine is the largest man-made source of radiation exposure in Western countries, accounting for a mean effective dose of 3.0 mSv per capita per year, comparable to the radiologic risk of 150 chest x-rays, and in many cases gonads fall in the imaging field, with > 20 millions examinations per year in US being abdominal and pelvic CT, and >0.5 million barium enema. Of the over 7 million workers exposed to medical radiation, special attention has been paid to those working in the interventional cardiology and radiology labs, with high and increasing professional exposures, two-to three times higher than diagnostic radiologists. Thus, adverse effects of radiation exposure are well worth of the scientific community’s interest. Aims of this review are: 1) to assess gonad dose to patients undergoing diagnostic testing or interventional fluoroscopy therapy and in professionally exposed interventional fluoroscopists; and 2) to evaluate the evidence linking radiation exposure in the low-to-moderate range (besides the radiotherapy high dose range) to adverse reproductive effects. In patients, the gonad radiation exposure can reach 5 mSv for a lower limb angiography, 20 mSv for a CT pelvis and hips, and 36 (in females) to 90 mSv (for males) for a lower gastrointestinal series. For interventional cardiologists, the gonad dose (below lead apron) is in the same order of magnitude of the shielded thyroid dose, with a median of 50 to 100 microSievert per cine-angiography procedure. The dose can be ten-fold higher for a complex interventional procedure. This leads to a cumulative exposure in the 0.5-1 Sv range over a professional lifetime of 30 years. At present, the epidemiological approach provided inconclusive results, inadequate for a robust evidence-based advice to exposed subjects, since large groups followed-up for decades would be required to detect a small increase in risk. A molecular epidemiology approach and/or the use of integrated biomarkers of reproductive health (e.h., reproductive hormone balance, sperm quality, sperm DNA damage) might be more fruitful in future research focused in the low-to-moderate dose range (< 1000 mSv) of greatest interest for diagnostic and professional exposures.