Feedback information for multiple serving cells are transmitted on high speed dedicated physical control channel (HS-DPCCH). A slot format for transmitting feedback information is determined based on the number of configured secondary serving cells and whether multiple input multiple-output (MIMO) is configured in the serving cells. Spreading factor is reduced to 128 when two secondary serving cells are configured and MIMO is configured in at least one of the two configured secondary serving cells, or when three secondary serving cells are configured. The serving cells are grouped into feedback groups, each feedback group having one or more serving cells. Channel coding may be applied to feedback information for the feedback groups. The resulting encoded feedback information for the feedback groups is concatenated to form composite feedback information.