The present study was conducted to determine the extent of possible damage and adverse effects on fiber and yam qualities characteristics of Egyptian cottons as subjected to mechanical manipulation by means of. gins, seed cotton cleaners and lint cleaners. The four Egyptian cotton varieties Giza 70, Giza 88 (extra long staple varieties), Giza 80 and Giza 89 (long staple varieties) were used as a material for this study. The seed cotton grade used was the same for each variety, i.e. Good- 1/4. The stick machine and inclined cleaner was used to dean seed cotton prior to ginning while the Mill-type lint opener cleaner was employed to dean cotton lint subsequent to ginning. (The Rotary Knife gin-stand and the McCarthy gin stand were used in this investigation). The findings of the present study indicated that when seed cotton cleaning and lint deaning were practiced in combination., the least amount of trash content was attained by both gin-stands. However, the reciprocating knife gin stand appeared to act better with the cleaning machineries than the Rotary Knife gin regarding the degree of deanliness of cotton attained. Further., fiber strength., elongation., length [ 2.5% S.L.) and length uniformity showed the highest decrease in their values when seed cotton deaning and lint cleaning were applied in combination. To the contrary, micrdnaire reading tended to increase whenever the cotton was processed by cleaning machineries. With respect to yarn quality properties, the results obtained revealed that the highest values of yarn strength were achieved when seed cotton deaning and lint cleaning were conducted in combination. This trend was the same for the 2 gin-stand types used in the study. By contrast, a general tendency of decrease in either the thick places or the thin places and hence an improvement in yam evenness could be noticed in the 2 gin-stands when cleaning both seed cotton and lint cotton were applied together. However nep count showed insignificant differences due to ginning and cleaning treatments.