A failure analysis was conducted on brass alloy 270 heat exchanger tubes that were pulled from a unit used to cool oil for the speed regulators and thrust bearings of a hydroelectric power plant. The tubes began to leak after approximately 5.5 years of service. Macrophotography and scanning electron microscopy were used to examine samples from the tubes. An energy-dispersive electron microprobe analysis was carried out to evaluate the zinc distribution. Results showed that the failure was due to dezincification. Replacement of the tubes with new tubes fabricated from a dezincification-resistant alloy was recommended.