Low‐capacitance (< 10 pF) Pb1−xSnxTe photodiodes operating near 77 °K (areas 1.7 × 10−4cm2) have been obtained via liquid‐phase epitaxial growth of low‐carrier‐concentration material (low 1014cm−3to high 1015cm−3). Response to a mode‐locked 1.06‐&mgr;m Nd:YAG laser with the devices terminated in 50 &OHgr; indicated a frequency response to 400 MHz. With a 14‐&OHgr; load and by exciting a photocurrent with radiation from a CO2laser, the shot noise rolloff point was found to be 1200 MHz. Optimum parameters have not yet been achieved, as evidenced by the increase in frequency response with increase in reverse bias; these results represent only a lower limit to this material's capability.