A microdialysis system for measuring the ethanol concentration curve in the nucleus accumbens of the rat brain was developed and tested in three different rat lines (AA, ANA, and Wistar) after an intraperitoneal (IP) and an intragastric (IG) dose of 1.0 g/kg ethanol. The flow rate of the modified Ringer solution was set at 5 microliters/min; samples were taken every minute after ethanol administration and analyzed with headspace gas chromatography. After IP administration, the brain ethanol levels rose much more rapidly than tail blood ethanol levels in the same animals. The maximum brain ethanol level after IG administration was lower and occurred later, and were similar to the tail blood levels in AA and ANA rats. No clear difference between the lines was found after IP administration but there was some indication that ANA rats may absorb alcohol after IG intubation faster than AA or Wistar rats.