A small high performance double focusing mass spectrometer employing a 90° electrostatic analyzer and a 60° magnetic analyzer is described. The radius of curvature of ion paths in the magnetic analyzer is 2 in. As a laboratory instrument for making gas or isotope analyses, its sensitivity and resolution make it competitive with instruments several times as large employing only a magnetic analyzer. With a permanent magnet the weight and power consumption are both low, making it attractive for applications where these factors may be of importance.