Two field experiments were carried out at Sakha Agricultural Re­search Station during 1996 and 1997 seasons on the new cotton culti­var Giza 89, to study the effect of hill spacing of 20,25 and 30cm (plant population) and plant growth alteration treatments i.e. topping , side branch bruning at 120 cm height, topping + pruning at 100cm height + pruning at 120 cm height on some vegetative and fruiting habits, earli­ness and seed cotton yield and its components. Generally the combined data clarified that wider hill spacing in­creased number of monopodia, main strem intemodes, sympodia, addi­tional fruiting branch bolls, retended bolls. fruiting sites, percentage of bolls on vegetative branches open bolls, boll weight and seed cotton-yield (Kintar/ fed.) while it decreased final plant height, number of aborted sites , days to finalt open boll, earliness percentage and number of unopen bolls. However , plant alteration treatments had a positive ef­fect on most studied traits and reverselly depressed number of monopo­dia, aborted sites and earliness percentage comparing with check. Within plant altering treatments, there are significant divergences. The results indicated that topping plants at 120cm height increased number of re-tended bolls, fruiting sites , days to first open-boll, open boll, unopen bolls and seed cotton yield (Kintar/fed.). Side branch pruning at 120 cm height increased final plant height, monopodia, main stem internodes, sympodia, earliness percentage and boll weight. Topping + pruning at 100cm height only decreased number of aborted sites. Topping + prun­ing at 120cm height increased additional fruiting branch bolls, percent­age of bolls on vagetative branches, boll weight and seed cotton yield (Kintar/fed.) Topping at 120 cm height and 30cm hill spacing which resulted in highest number of retended bolls and seed cotton yield.