This study investigated the instructional assessment practices, techniques, and challenges of science teachers in Barbados with a view to providing baseline data on the state of the art of this important aspect of science teaching. A total of 55 science teachers drawn from 12 out of 22 secondary schools in Barbados constituted the participants in the study. The self report data obtained by a survey questionnaire revealed that teachers use similar instructional assessment practices regardless of sex, teaching experience, professional qualification, or academic qualification. Teachers reported using collaborative and formative assessment practices most often, although the techniques they reported using did not greatly reflect this. Idiosyncratic solutions to their systemic challenges do not reflect the teachers' claim of using collaborative assessment practices. Based on the findings, it is recommended that teachers will benefit from professional development activities that promote reflection and collaboration in addressing their instructional assessment challenges on a practical level. Further research is necessary to look into the influence of teacher beliefs and attitudes on their instructional assessment practices.