Low incident light and high temperatures in the tropics limit grain filling periods. There is little evidence in genetic advance for grain filling rate and duration in tropical maize. The study seeks to characterize the rate and duration of grain development in elite tropical maize under the short days, low light and high temperatures of Hawaii. The specific objectives were to determine variation, gene effects for grain filling rate (GFR), grain filling duration (GFP), chlorophyll concentration (SPAD), and other agronomic traits among 8 inbreds and 28 hybrids. Correlations were determined among GFR, GFP, SPAD and other agronomic traits. The inbreds and F1 diallele hybrids were grown in 3 plantings across the year in Waimanalo, HI using RCB designs with 2 reps. To determine GFR and GFP, ears were harvested at weekly intervals from 2 weeks after 50% midsilk and a final harvest at 6 weeks. Significant differences for GFR (P<0.01), GFP (P<0.05), kernel number and rows (P<0.01) were observed for the inbreds and hybrids. Heterosis effects were also significant for GFR (P<0.01) and GFP (P<0.05). GFR (g/100 kernels/day) ranged widely from 0.470 to 1.217 for the hybrids and 0.571 to 1.008 for the inbreds. The additive type of gene action was predominant for GFR, kernel rows, and SPAD, while non-additive gene effects were more prevalent in GFP and kernel number. No significant correlations were found between GFR and GFP, GFR and days to anthesis and silk. GFR explained 31.10% and 27.31% of the variation (P<0.01) in the weight per ear for both hybrids and inbreds, respectively. The study reveals that recurrent selection methods may be appropriate to increase GFR together with the hybrid breeding approach to extend the GFP.