Screening of microbial natural products continues to represent an important route to the discovery of novel bioactive compounds for the development of new therapeutic agents, and actinomycetes are still the major producers of biopharmaceuticals. Selective isolation of bioactive actinomycete species, in particular the rare ones, has thus become a target for industrial microbiologists. In this context, bacteriophages have proven to be useful tools as (1) naturally present indicators of under-represented or rare actinomycete taxa in environmental samples, (2) indicators of the relatedness of bioactive taxa in target-directed search and discovery, (3) de-selection agents of unwanted taxa on isolation plates in target-specific search for rare actinomycete taxa, (4) tools in screening assays for specific targets. Against this background, a number of case studies are presented to illustrate the use of bacteriophages as tools in actinomycete-origin bioactive compound search and discovery programs.