Testosterone suppression, achieved through orchiectomy or medically induced androgen-deprivation therapy (ADT), is a standard treatment for men with recurrent and metastatic prostate cancer. Current assay methods demonstrate the capacity for testosterone suppression to <0.7 nmol/l, and clinical data support improved outcomes from ADT when lower levels are achieved. Practical clinical guidelines are warranted to facilitate adoption of 0.7 nmol/l as the new standard castrate testosterone level. A pan-Canadian group of experts, representing diverse clinical specialties, identified key clinical issues, searched and reviewed relevant literature, and developed consensus statements on testosterone suppression for the treatment of prostate cancer. The expert panel found that current evidence supports the clinical benefit of achieving low testosterone levels during ADT, and encourage adoption of ≤0.7 nmol/l as a new castrate level threshold. The panel recommends regular monitoring of testosterone (e.g., every 3–6 months) and prostate-specific antigen (PSA) levels as clinically appropriate (e.g., every 3–6 months) during ADT, with reassessment of therapeutic strategy if testosterone is not suppressed or if PSA rises regardless of adequate testosterone suppression. The panel also emphasizes the need for greater awareness and education regarding testosterone assay specifications, and strongly promotes the use of mass spectrometry-based assays to ensure accurate measurement of testosterone at castrate levels.