Pima S-6, Gossypium barbadense L., was planted at two locations at Maricopa, AZ for collection of data to be used in the development of a plant growth model for Pima cotton. Location one consisted of 25 four-row Plots, 13.4m long, planted on 6 April 1990. Location two was a 14.3 ha commercial field planted on 4 April 1990. Growth measurements and phenological events, i.e. dates of emergence, first square, first bloom, etc. were recorded at each location. Flowers were tagged periodically on plants in plots at location one to estimate boll development rates and total maturation times from anthesis to boll-opening. Meteorological data from seven weather stations in Arizona for the 1988 and 1989 growing seasons were obtained for validation of the model. Plant growth during the first 5 weeks after emergence at location one was slow. Plant height increased rapidly during the first week of June and continued until the first week of July. Plants grew significantly faster after the second week of July and reached a height of 1.1 to 1.6m by the middle of August. The formation of squares decreased significantly by the first week of August. The boll load, as recorded in the first week of August, varied from 15 to 30 p^-1. The variation of fruit load is attributed to high temperatures in the last week of June, i.e., greater than 40 C for six or more hours of the day which resulted in significant abscission of flowers and young squares. The emergence of seedlings at location two was not uniform until 10 to 15 days after planting due to relatively low night temperatures. One hundred and fifty plants were mapped the second week of May to select a uniform portion of the experimental area. Subsequently, 125 plants were measured periodically for growth and development. It is anticipated that additional field data will be needed from other Pima growing areas to obtain replicate data sets for validation of the Pima model.