Inclusion Criteria:

- Histologic proof of Grade 1, 2, or 3a follicular lymphoma (FL) without clinical or
pathological evidence of transformation

- Previously treated with at least 2 prior lines of therapy, including at least 1
rituximab combination chemotherapy regimen; last prior line of therapy includes an
anti CD20 monoclonal antibody-containing chemotherapy regimen (separate lines of
therapy are defined as different regimens that are either separated by disease
progression, refractory disease, or relapsed disease)

- Resistant disease to the last therapy, defined as progression of disease during or
within 12 months of the last dose of a CD20 antibody combination chemotherapy regimen

- At least 1 measurable site of disease according to International Working Group
Revised Response Criteria for Malignant Lymphoma

- Eastern Cooperative Oncology Group performance status grade 0 or 1

- Hematology and biochemical laboratory values must be within protocol-defined
parameters within 7 days prior to enrollment

- Agrees to protocol-defined use of effective contraception

- Women of childbearing potential must have a negative serum or urine pregnancy test at
screening

Exclusion Criteria:

- Prior nitrosoureas within 6 weeks, chemotherapy within 3 weeks, therapeutic
anticancer antibodies within 4 weeks, radio- or toxin-immunoconjugates within 10
weeks, radiation therapy or other investigational agents within 3 weeks, or major
surgery within 4 weeks of first dose of study drug

- Prior treatment with PCI-32765, other Bruton's tyrosine kinase inhibitors, or
phosphoinositide 3-kinase delta inhibitors

- Concurrent enrollment in another therapeutic investigational clinical treatment study

- Received a prior allogeneic hematopoietic stem cell transplant (prior autologous
hematopoietic stem cell transplant is allowed)

- Known central nervous system lymphoma

- History of prior malignancy (except malignancy treated with curative intent and with
no known active disease present for >=3 years before enrollment, adequately treated
non-melanoma skin cancer or lentigo maligna without evidence of disease, or
adequately treated cervical carcinoma in situ without evidence of disease)

- History of stroke or intracranial hemorrhage within 6 months prior to enrollment

- Requires anticoagulation with warfarin or equivalent vitamin K antagonists

- Requires treatment with strong cytochrome P450 (CYP)3A4/5 inhibitors

- Clinically significant cardiovascular disease such as uncontrolled or symptomatic
arrhythmias, congestive heart failure, or myocardial infarction within 6 months of
screening, or any Class 3 (moderate) or Class 4 (severe) cardiac disease as defined
by the New York Heart Association Functional Classification

- Known history of Human Immunodeficiency Virus (HIV) or Hepatitis C or active
infection with Hepatitis B or any uncontrolled active systemic infection requiring
intravenous antibiotics

- Women who are pregnant or breastfeeding

- Any life-threatening illness, medical condition, or organ system dysfunction which,
in the investigator's opinion, could compromise the patient's safety, interfere with
the absorption or metabolism of PCI-32765 capsules, or put the study outcomes at
undue risk