In an effort to characterize the effectiveness of cardiology consultation, the outcomes of consultants' recommendations for diagnostic actions and cardiac drugs were quantitatively examined in 394 cases. Drug recommendations were made more frequently (49 percent) than diagnostic recommendations (38 percent) and were associated with a higher rate of concordance (82 percent to 64 percent). Recommendations to start therapy with a drug, especially an antihypertensive or an antianginal, were associated with a lower concordance rate than recommendations to continue or discontinue drug therapy. Consultees' responses to recommendations for diagnostic action did not vary significantly according to the type of action suggested. Nonconcordance with diagnostic suggestions was particularly high when a service made a large number of consult requests. Concordance was increased if the consultant left a follow-up note. Consultees' responses to drug and diagnostic recommendations were independent of one another. The study represents the first systematic assessment of cardiology consultation activities and provides a methodology for subsequent studies.