Mepiquat chloride (1,1-dimethyl-piperidinium chloride) is a plant growth regulator that can be used by producers to manage crop development, uniformity, and maturity. Field experiments were conducted from 1998 to 2000 to evaluate the effect of row spacing and mepiquat chloride applications on cotton (Gossypium hirsutum L.). Four rates of mepiquat chloride (4 x 0.29 L ha-1, 2 x 0.58 L ha-1, 4 x 0.58 L ha-1, and 4 x 0.88 L ha-1) were evaluated for cotton grown in 19-, 38-, and 76-cm rows in 1998 and 25-, 38-, and 76-cm rows in 1999 and 2000. In 1999 and 2000, plant heights and number of total main stem nodes were different among row spacings and mepiquat chloride applications. The height-to-node ratio was highest in plots not receiving mepiquat chloride. Cotton grown in narrow rows had higher seed cotton yields than cotton produced in 76-cm rows, but reduced gin turnout in narrow row spacings negated any increase in seed cotton yield. As a result, lint yields among the different row spacings were not significantly different in 2 of 3 yr. In general, reduced row spacing and mepiquat chloride application did not lower fiber quality. In some cases, micronaire was reduced in narrow row spacings, but values were within the acceptable range for fiber grade standards to avoid discounts. Applications of mepiquat chloride increased lint yield only 1 of 3 yr, but is still considered a desirable management tool to control crop growth for efficient harvest, especially on fields with a history of excessive vegetative growth. Ultra-narrow row systems appeared to be a viable alternative to traditional wide-row systems for cotton production in the Mississippi Delta.