Free-space optics (FSO) is a technology that uses modulated optical beams to transmit information in a line-of-sight fashion to achieve a high-bandwidth communications link. FSO technology has been investigated for military and civilian “last mile” applications for many years and, more recently, has generated interest for space-based applications. As the use of FSO technology grows, the potential for optical interference that degrades FSO network performance, whether intentional (jamming) or otherwise, becomes a matter of increasing importance. The investigation described in this paper examined the effects of interference upon the operation and performance of a point-to-point FSO link connecting two virtual local area networks. The sources of interference were laser pulses of varying energy, wavelength, and repetition rate produced from a nitrogen-pumped, tunable dye laser. The study evaluated the effect upon FSO link performance of varying the output power of the interfering source for a fixed wavelength, of varying the wavelength of the source for a fixed power, and of varying the pulse repetition rate of the source. The results of the study indicated that FSO link performance was negatively influenced by such interference.