A triaxial accelerometer used as an inclinometer (INC) (Logger Technology, Sweden) needed to be evaluated for field measurements of arm postures and movements. INC consists of one portable data logger and up to four sensors. Each sensor measures the inclination to the vertical line. The sampling frequency is 20 Hz and, the logger can collect data for up to 12 h. The aim of the present study was to compare INC measurements with those from an optoelectronic measuring system- the Mac Reflex system (OPT) (Qualisys AB, Sweden). For all movements with normal to high velocities INC measured the degree of arm elevation with very high precision. At very high velocities and, especially when the direction of the velocity was perpendicular to the vertical line the largest differences between INC and OPT were found. In field studies INC has proved to be very safe and useful in assessment of arm movements. INC was easy to handle and easy to wear for the researcher and the subject, respectively.