Superheated drop detectors (SDDs) have been developed for individual neutron monitoring. An SDD using 1-butene(C 4 H 8 ) as the neutron sensitive liquid was exposed to Am-Be neutrons and the dependence of the detection sensitivity on pressure was measured. The pressure-dependent sensitivity was calculated for the 1-butene SDD exposed to Am-Be neutrons and compared with the measurements. The results are discussed in relation to bubble formation theory. A parameter involved in the sensitivity calculation based on the theory was determined by comparing the measured characteristics of the pressure-dependent sensitivity with the calculations.