The temporal dynamics of penicillin and erythromycin co-resistance in Streptococcus pneumoniae based on two extensive multicentre Spanish surveillance SAUCE studies (1996-1997 and 1998-1999) is presented. Erythromycin resistance among penicillin non-susceptible isolates seems to have reached a limit as evidenced by a null increase between the two surveys, whereas it is growing among penicillin-susceptible pneumococci.