Tar oil was prepared as soluble liquid 95% and tested against the two stages of eggs and newly hatched larvae of the pink bollworm, Pectinophora gossypiella (Saunders) in the laboratory as well as determining the total of protein, carbohydrate and lipids in the 4th instar larvae of the pink bollworm treated as newly hatched. In field experiment, the formulated tar oil tested against the pink and spiny bollworms infested cotton crop in 2011 and 2012 cotton seasons in Beni Suef Governorate by spraying the cotton plants twice at 14 day interval using concentrations of 1.5 and 2%. Infestation percentages were determined immediately before spraying and weekly after spraying then reduction percentages were calculated.The obtained results in the laboratory studies indicated that the toxicity of the prepared tar oil 95% soluble liquid was the most ovicidal action against the 4-day old eggs, followed by 3-day, 2-day and 1-day old eggs of the pink bollworm. On the other hand, the toxicity of tar oil against the newly hatched larvae increased with elapse the time after treatment. Determination of the biochemical contents showed that total protein and carbohydrates in the larvae that had values near from the control. While, total lipids in treated larvae had similar value unsingnificantly different from the control. In field study, the formulated tar oil concentrations showed more activity against pink bollworm than spiny bollworm since it gave seasonal reduction percentage in infestation 55.69 & 67.09% and 47.52 & 62.45% at concentrations of 1.5 and 2% against pink bollworm during the seasons of 2011 & 2012. In case of spiny bollworm, the reduction percentage were 37.49 & 50% and 27.98 & 58.46% for concentrations 1.5 and 2% during seasons of 2011 & 2012. Generally, it could be concluded that the two tested concentrations 1.5 and 2% had slightly to moderately effect in controlling the two bollworms since they gave seasonal reduction average in infestation 50.2 & 62.19% and 41.08 & 61.15% during the seasons of 2011 & 2012 against the two pests.