The reaction conditions are described for preparation and gas chromatographic analysis of microgram quantities of the trimethylsilyl (TMS) esters of 3,6-dichloro-o-anisic acid (dicamba), (2,4-dichlorophenoxy)acetic acid (2,4-D), (2,4,5-trichlorophenoxy)acetic acid (2,-4.5-T), and 2 water-degradable polymers of 2,4,5-T. Silylation was efficient at 0, 22, and 55°C. A ratio of 1:10 silylating agent (N,O-bis-(trimethylsilyl)acetamide, BSA) to silylation solvent (dimethylformamide, DMF) was optimum for silylation of 2,4-D, 2,4,5-T, and 2,4,5-T polymers. A 1:50 ratio was best for silylation of dicamba. A 1:10 ratio (BSA/DMF) will tolerate up to 1.0 and 0.1% water in the silylation of 2,4-D and 2,4,5-T, respectively. A 1:50 ratio will tolerate up to 0.1% water in the silylation of dicamba. Silylated samples could be analyzed immediately after addition of the silylation reagent. Stability of silylated samples at 22°C was directly proportional to concentration; 1.0 μg samples showed no loss of activity 2.3 hr after reaction. TMS esters were chromatographed on a 6′ × ¼″ glass column containing 3% SE-30 on 80-100 mesh Chromosorb W(HP) at 230°C.