The pharmacokinetics of aztreonam were studied in 12 healthy male volunteers aged 65 to 75 years who received 1 g of the antibiotic intravenously. Data were fitted to a two-compartment open model to yield the following parameters: t 1/2, lambda 1, 0.15 h; t 1/2,z, 2.06 h; area under the 24-h serum concentration-time curve, 231.8 micrograms ml-1 h; Cmax, 120.1 micrograms/ml; V1 area, 0.16 l/kg; and serum clearance, 0.94 ml min-1 kg. Twenty-four hour urinary elimination reached 63.1% of dose as aztreonam and 3.1% as the open ring metabolite SQ 26,992. These data were similar to those obtained for healthy males aged 18 to 35 years. Thus, age per se is not a major therapeutic consideration in treating elderly patients, and other factors, primarily the parameters of renal function, should serve as the basis for any dose reduction.