Dermestid larvae, Trogoderma versicolor (Creutzer), and adult American cockroaches, Periplaneta americana (Linné), were affected by ruby laser pulses of two intensities, 0.06 ± 0.04 per 10−7 second duration and 0.57 ± 0.06 joules per 0.2 milliseconds. Laser impact areas were 1.5 mm. in diameter. The first intensity, directed at cephalic regions of dermestid larvae, caused mortality in 3–48 hours. The same intensity directed at larval mid-abdominal areas caused visible outer integument and body-hair scorching, cessation of feeding, growth rate, and movement, and loss of negative phototactic responses. Directed at posterior abdominal regions of larvae, it caused damage to the epidermal layer noticeable in four succeeding moults. It caused temporary (10-15 min.) immobility and loss of negative phototaxis when directed at pro-thoracic regions of cockroach adults. P. americana adults were more severely affected by the second laser treatment, exhibiting immobility, loss of negative phototaxis, and cessation of eating. Total mortality in the five treated specimens occurred in 8-14 days as compared with 45-68 days in controls.