The concept of biologically modified carbon paste is shown to be very attractive for the design and operation of miniature bioelectrodes. In particular, tissue-containing carbon paste microelectrodes combine the ease of fabrication, with fast response times, high sensitivity and low cost. The very fast response is attributed to the close proximity of the biocatalytic and sensing sites. These features are illustrated using a mixed banana/carbon-paste microelectrode that offers selective and sensitive determination of dopamine. The performance of this microelectrode is further enhanced by using high-speed background subtraction square-wave scanning. The suitability of this electrode for in-vivo and in-vitro studies of brain chemistry is discussed. Other biosensing applications may benefit from such coupling of the technologies of surface modification and miniaturization.