Infrared solar absorption spectra recorded at 0.02-cm-1 resolution during a balloon flight from Alamogordo, N.M. (33¿N), on March 23, 1981, have been analyzed for the possible presence of absorption by formic acid (HCOOH). An absorption feature at 1105 cm-1 has been tentatively identified in upper tropospheric spectra as due to the &ngr;6 and Q branch. A preliminary analysis indicates a concentration of ≈0.6 ppbv and ≈0.4 ppbv near 8 and 10 km, respectively.