Monitoring of cotton with COTMAN^TM is a useful management tool, but data are needed from ultra-narrow-row (UNR) cotton to evaluate the need to recalibrate COTMAN reference curves for this cropping system. The objectives of this study were to compare vegetative growth, reproductive development, cutout, boll set, and lint yields of UNR (7.5-inch) and wide-row (40-inch) cotton. 'Paymaster 1220 RR' was planted in ultra-narrow and wide-rows on May 9, 1998 at the Milan (TN) Experiment Station in a RCB design. Growth and development were monitored with COTMAN. Development and days to cutout (5 nodes above white flower, or NAWF=5) differed markedly between ultra-narrow and wide-row cotton. Plants in UNR were much shorter, earlier maturing, and more determinate than those in wide rows. Plants in wide rows reached cutout during the third week of flowering, when about 35% of first-position sites had set bolls. Plants in UNR reached NAWF=5 during the first week of flowering, when fewer than 20% of first-position sites had set bolls. Most bolls in UNR were set after that time. Thus NAWF=5 did not represent the last effective boll population in this UNR cotton. The cutout reference point used by COTMAN may need to be changed to better represent the last effective boll population in UNR cotton.