A 12-category instrument was developed for describing verbal interaction among students working in small groups in the biology laboratory. Seventy-five student laboratory groups were tape recorded. Data were collected while the students worked on two different laboratory activities, and group laboratory reports were collected at the end of each recording session. The tapes were used to establish intercoder agreement in the use of the instrument. The laboratory reports were evaluated by five experienced biology teachers, and the total score taken as an indication of task orientation of the group. Spearman's rho was used to determine the correlations between task orientation and the percentages of interaction classified in each category of the observation instrument, and between measures for the two different laboratory activities. (EB)