The increase is small.

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J Hypertens. 2005 May;23(5):921-8.

Blood pressure response to chronic intake of coffee and caffeine: a
meta-analysis of randomized controlled trials.

Noordzij M, Uiterwaal CS, Arends LR, Kok FJ, Grobbee DE, Geleijnse JM.

Division of Human Nutrition, Wageningen University, Wageningen bJulius
Center for Health Sciences and Primary Care, Utrecht University, Utrecht,
The Netherlands.

PURPOSE: Coffee is a widely consumed beverage and small health effects of
substances in coffee may have large public health consequences. It has been
suggested that caffeine in coffee increases the risk of hypertension. We
performed a meta-analysis of randomized controlled trials of coffee or
caffeine and blood pressure (BP). DATA IDENTIFICATION: BP trials of coffee
or caffeine published between January 1966 and January 2003 were identified
through literature databases and manual search. STUDY SELECTION: A total of
16 studies with a randomized, controlled design and at least 7 days of
intervention was selected, comprising 25 strata and 1010 subjects. DATA
EXTRACTION: Two persons independently obtained data on sample size, type and
duration of intervention, changes in BP and heart rate (HR), and subjects'
characteristics for each trial. Meta-analysis was performed using a
random-effects model. RESULTS: A significant rise of 2.04 mmHg [95%
confidence interval (CI), 1.10-2.99] in systolic BP and 0.73 mmHg (95% CI,
0.14-1.31) in diastolic BP was found after pooling of coffee and caffeine
trials. When coffee trials (n = 18, median intake: 725 ml/day) and caffeine
trials (n = 7, median dose: 410 mg/day) were analysed separately, BP
elevations appeared to be larger for caffeine [systolic: 4.16 mmHg
(2.13-6.20); diastolic: 2.41 mmHg (0.98-3.84)] than for coffee [systolic:
1.22 mmHg (0.52-1.92) and diastolic: 0.49 mmHg (-0.06-1.04)]. Effects on HR
were negligible. CONCLUSIONS: Regular caffeine intake increases BP. When
ingested through coffee, however, the blood pressure effect of caffeine is
small. PMID: 15834273

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstra
ct&list_uids=15834273&query_hl=5&itool=pubmed_docsum

It depends on the person. Caffiene doesn't seem to affect my blood pressure.
But it may affect other people's blood pressure more.

Jeff