Several previous papers have been published about radioactive contamination in Mexican soil, marine sediments and foodstuffs. Ever since, results have been according to expectation, mainly consisting of natural isotopes in small concentration. Continuous research leads with the surprising finding of fission product 137 Cs (t 1/2 = 30 years) in strawberries produced in different states, about 2000 km away from each other. Never before, such contaminant has been observed in foodstuffs, produced in this country. The aim of this work is to report the presence of 137 Cs in Mexican strawberries and compare the activity of such contaminant with the natural radioactivity of 40 K (t 1/2 = 1.28 × 10 9 years), through gamma spectrometry. Eventually, the specific activity of 137 Cs observed in samples FM4, FM5 and FBC is respectively 0.7, 0.8 and 0.3 Bq/kg. The limits established in CODEX- STAN-193-1995 for 137 Cs are 1000 Bq/kg, so all samples meet the recommendation. It's presence now in vegetables result with enough interest to be known and considered in the near future to measure the possible effect that radioactive contamination could reach after nearly 80 years from second world war, where no nuclear test has been performed, nuclear accident occurred, neither nuclear weapon has ever been used.