We recorded echolocation and ultrasonic social signals of the bat Myotis septentrionalis. The bats foraged for insects resting on or fluttering about an outdoor screen to which they were attracted by a 'backlight'. The bats used nearly linearly modulated echolocation signals of high frequency (117 to 49 kHz) with a weak second harmonic. The orientational signals from patrolling bats were about 2.4 ms in duration and occurred at a repetition rate of about 18 Hz. The signals used by bats as they approached the screen were of shorter duration (0.72 ms) and occurred at higher rates (33.8 Hz). We registered one feeding 'buzz'. We recorded social signals when two bats patrolled the hunting area. The social signals were characterized by their longer durations (6 ms), lower frequencies (70 to 30 kHz), and curvilinear sweeps. We calculated the source levels of orientational and social signals using the differences in arrival times at three microphones in a linear array. The source levels were on average 102dB peSPL at 10 cm. We could not calculate source levels of the signals used by bats as they approached the screen at close range, but these signals were much weaker (about 65d8 peSPL at the microphone).