Abstract: Mepiquat chloride (1, 1-dimethyl-piperidinium chloride) as a plant growth regulator that can used by producer to manage the crop development, uniformity and maturity. Field experiments conducted during 2002 and 2003 to evaluate the fact of row spacing and Mepiquat chloride application on cotton (Gossypium hirsutum L.) var. MNH-700. Four rates of Mepiquat chloride (4x123, 2x246, 4x246 and 4x370 mL ha^-1) and a check with 0 mL ha^-1 were evaluated for cotton growing in 25, 50 and 75 cm row spacing in 2002 and 2003. Plant height and number of total main stem nodes were different among row spacing and Mepiquat chloride application. The height was highest in plots where no application of Mepiquat chloride. Cotton grown in narrow row spacing (20 and 50 cm) had higher seed cotton yield than 75 cm row spacing, but reduce Ginning Out Turn (GOT) percentage in narrow row spacing negating any increase in seed cotton yield. In general reduced row spacing and Mepiquat chloride application did not lower fiber quality. In some cases, micronair was reduced in narrow row spacing (0.1), but values were in acceptable range for fiber traits. Mepiquat chloride is considered a desirable management tool to control crop growth. Ultra-narrow row spacing should practices only in the areas where plant growth is not accurate or upto the standard. In fertile soils, Mepiquat application is suggested for control of plant growth in efficient way under narrow row spacing in viewing the habit of cotton genotype.