There are many clinical situations in which IV access is unavailable, and the endotracheal route is a valuable alternative route for drug therapy. The optimal technique of endotracheal drug administration, however, has not been determined. Twenty-nine dogs were divided into five groups and given endotracheal lidocaine at two doses, 2 mg/kg and 4 mg/kg, by differing techniques: control, undiluted lidocaine in a syringe was given as a bolus; needle, the drug was given through a needle attached to the syringe; dilution, lidocaine was diluted approximately 1:1 with normal saline and the entire dilution was given as a bolus; normal saline (NS) followup, lidocaine in a syringe was given as a bolus, followed immediately by an equal bolus of normal saline; and catheter, the drug was given through a catheter that was placed inside and extended just beyond the endotracheal tube. Mean plasma lidocaine levels (microgram/mL) at five minutes were as follows (at a 2-mg/kg endotracheal lidocaine dose): control, 0.64; needle, 0.0; dilution, 3.1; and (at a 4-mg/kg endotracheal lidocaine dose) control, 1.0; needle, 0.6; dilution, 6.2; NS followup, 1.9; and catheter, 1.9. At all time periods with either dose of lidocaine (2 or 4 mg/kg), the highest plasma lidocaine levels occurred with dilution and the lowest with the needle method. These results were highly significant (P less than .001). The highest plasma lidocaine levels may be attained by diluting the drug with normal saline. Higher levels were achieved when the drug was given through a catheter or when the drug was followed with a bolus of normal saline.(ABSTRACT TRUNCATED AT 250 WORDS)