The aim of this study was to investigate quality coding of blend ratios of binary mixtures by olfactory receptor cells in the spiny lobster. Three odorants (adenosine-5'-monophosphate, L-glutamate, and taurine) at 0.1-100 mumol.1(-1) and seven blend ratios of each of their binary mixtures at a total concentration of 100 mumol.1(-1) were used. The olfactory cells recorded (n = 48) evoked across-neuron patterns for single odorants that were well separated from each other. Across-neuron patterns varied with stimulus concentration but less than with stimulus type. Blend ratios of the three mixtures evoked across-neuron patterns that were orderly placed within a continuum between those elicited by the components. Mixture interactions, defined as a lack of independent effects by a mixture's components, occurred in 25, 24 and 37% of responses to blend ratios of glutamate/taurine, adenosine-5'-monophosphate/taurine, and glutamate/adenosine-5'-monophosphate, respectively. These mixture interactions did not have a large enough effect on the across-neuron patterns for the mixtures such they would be novel relative to those of the single components. These results suggest that despite mixture interactions the quality of individual compounds is not lost when mixed. This corroborates behavioral studies showing that spiny lobsters have the ability to elementally process odor mixtures.