The growth rate of queen conch cultured in pens was studied from October 1993 to March 1994. Sixteen pens (50 m2 each, four pens per environment), were set in four environments: Thalassia, Thalassia-sand, Sand and Coral within a reef lagoon on Punta Gavilan and Banco Chinchorro. Twenty conchs were introduced in each pen (sizes: 100-120, 120-140, 140-160 and 160-180 mm shell length) and measured monthly to the nearest mm. Growth rate was assessed by two methods: a) shell marginal mean increase and b) the Gulland-Holt method considering all conch within pens. In the first method, the environment Sand had the highest growth (3.21 +/- 0.26 mm/month) at Punta Gavilan, whereas at Banco Chinchorro, highest growth was recorded in Coral (2.31 +/- 0.44 mm/month). Considering the second method, highest asymptotic length conch in Punta Gavilan occurred in Thalassia-sand (287.5 mm), whereas in Banco Chinchorro the highest asymptotic length was measured in Sand (318.1 mm). There were significant differences in growth between sites; juvenile growth is related with habitat quality mainly food availability.