Monthly samplings between September 1988 and June 1989 were carried out at Costa Verde (Cienaga, Colombia) to obtain juveniles and adults of the sea bob Xiphopenaeus kroyeri. Physical-chemical data (salinity, temperature, oxygen) of the bottom water and transparency of the water column were also taken. The gonadal developmental stages of each individual were determined. It was found that the greatest abundance of mature females occured in December, and that from January to April spawned females appeared. The minimal total length at maturation for females was determined as 77.5 mm, and for males as 67.5 mm. Sex ratio was always skewed towards males; its total value was 1: 0.7.