Experimental manipulationofthe upper bound on the retention interval (30 sec, with average duration of 11 sec, vs. 2 min, with average duration of 18 sec) failed to produce evidence for independent adjustment of initial long-term and short-term storage strengths. Very accurate strength functions of retention time were obtained; these were fitted equally well by a two-component equation and a one-componentequation derived from a theory postulating sequential employment of an active attentional buffer and a one-trace passive storage system. The latter theory appears to be capable of accounting for both post-attentional and two-phase experimental strength data, using fewer free parameters than strength theories which postulate the simultaneous existence of short-term and long-term traces. Other arguments for two traces are also discussed In relation to the postulate of a single post-attentional trace.